If A+B+C=π, Prove that: Sin(B+C−A)+Sin(C+A−B)+Sin(A+B−C)=4SinASinBSinC

In this article, we will explore a mathematical problem involving trigonometric functions. The problem states that if A+B+C=π, we need to prove that Sin(B+C−A)+Sin(C+A−B)+Sin(A+B−C)=4SinASinBSinC. This problem requires the application of trigonometric identities and the use of algebraic manipulations.
To tackle this problem, we need to recall some basic trigonometric identities. The sum and difference formulas for sine are given by:
Sin(A+B)=SinACosB+CosASinB
Sin(A−B)=SinACosB−CosASinB
We will also use the identity Sin(π−A)=SinA.
We start by using the sum and difference formulas for sine to expand the three terms in the left-hand side of the equation:
Sin(B+C−A)+Sin(C+A−B)+Sin(A+B−C)
=SinBCosC+CosBSinC−SinA+SinCCosA+CosCSinA−SinB+SinACosB+CosASinB
Now, we can simplify the expression by combining like terms:
=(SinBCosC+CosBSinC+SinCCosA+CosCSinA+SinACosB+CosASinB)−2SinA
Next, we can use the angle addition formula for sine to simplify the expression further:
=(Sin(B+C)+Sin(A+C)+Sin(A+B))−2SinA
Now, we can use the fact that A+B+C=π to simplify the expression:
=(Sin(π−A)+Sin(A+C)+Sin(A+B))−2SinA
=(SinA+Sin(A+C)+Sin(A+B))−2SinA
Next, we can use the angle addition formula for sine to simplify the expression further:
=(SinA+SinACosC+CosASinC+SinACosB+CosASinB)−2SinA
Now, we can simplify the expression by combining like terms:
=(SinA+SinA(CosC+CosB)+CosA(SinC+SinB))−2SinA
Next, we can use the angle addition formula for cosine to simplify the expression further:
=(SinA+SinACos(C+B)+CosASin(C+B))−2SinA
Now, we can use the fact that A+B+C=π to simplify the expression:
=(SinA+SinACos(π−A)+CosASin(π−A))−2SinA
=(SinA+SinACosA+CosASinA)−2SinA
Next, we can simplify the expression by combining like terms:
=(SinA+SinACosA+CosASinA)−2SinA
=SinA+SinACosA+CosASinA−2SinA
Now, we can use the fact that SinACosA=21Sin(2A) to simplify the expression:
=SinA+21Sin(2A)+CosASinA−2SinA
Next, we can simplify the expression by combining like terms:
=SinA+21Sin(2A)+CosASinA−2SinA
=21Sin(2A)+CosASinA−SinA
Now, we can use the fact that CosASinA=21Sin(2A) to simplify the expression:
=21Sin(2A)+21Sin(2A)−SinA
Next, we can simplify the expression by combining like terms:
=21Sin(2A)+21Sin(2A)−SinA
=Sin(2A)−SinA
Now, we can use the angle addition formula for sine to simplify the expression:
=Sin(A+A)−SinA
=Sin(2A)−SinA
Next, we can use the fact that Sin(2A)=2SinACosA to simplify the expression:
=2SinACosA−SinA
Now, we can factor out SinA from the expression:
=SinA(2CosA−1)
Next, we can use the fact that CosA=21(1+Cos(2A)) to simplify the expression:
=SinA(221(1+Cos(2A))−1)
=SinA(1+Cos(2A)−1)
Now, we can simplify the expression by combining like terms:
=SinACos(2A)
Next, we can use the fact that Cos(2A)=2Cos2A−1 to simplify the expression:
= \operatorname{Sin} A (<br/>
**Q&A: If $A + B + C = \pi$, Prove that: $\operatorname{Sin}(B + C - A) + \operatorname{Sin}(C + A - B) + \operatorname{Sin}(A + B - C) = 4 \operatorname{Sin} A \operatorname{Sin} B \operatorname{Sin} C$**
Q: What is the given equation and what needs to be proved?
A: The given equation is A+B+C=π, and we need to prove that Sin(B+C−A)+Sin(C+A−B)+Sin(A+B−C)=4SinASinBSinC.
Q: What are the basic trigonometric identities used in the proof?
A: The basic trigonometric identities used in the proof are the sum and difference formulas for sine, which are given by:
Sin(A+B)=SinACosB+CosASinB</span></p><pclass=′katex−block′><spanclass="katex−display"><spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mimathvariant="normal">Sin</mi><mo></mo><mostretchy="false">(</mo><mi>A</mi><mo>−</mo><mi>B</mi><mostretchy="false">)</mo><mo>=</mo><mimathvariant="normal">Sin</mi><mo></mo><mi>A</mi><mimathvariant="normal">Cos</mi><mo></mo><mi>B</mi><mo>−</mo><mimathvariant="normal">Cos</mi><mo></mo><mi>A</mi><mimathvariant="normal">Sin</mi><mo></mo><mi>B</mi></mrow><annotationencoding="application/x−tex">Sin(A−B)=SinACosB−CosASinB</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mopen">(</span><spanclass="mordmathnormal">A</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">−</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mclose">)</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7667em;vertical−align:−0.0833em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal">A</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Cos</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">−</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6833em;"></span><spanclass="mop"><spanclass="mordmathrm">Cos</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal">A</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span></span></span></span></span></p><p><strong>Q:Howistheexpression<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mimathvariant="normal">Sin</mi><mo></mo><mostretchy="false">(</mo><mi>B</mi><mo>+</mo><mi>C</mi><mo>−</mo><mi>A</mi><mostretchy="false">)</mo><mo>+</mo><mimathvariant="normal">Sin</mi><mo></mo><mostretchy="false">(</mo><mi>C</mi><mo>+</mo><mi>A</mi><mo>−</mo><mi>B</mi><mostretchy="false">)</mo><mo>+</mo><mimathvariant="normal">Sin</mi><mo></mo><mostretchy="false">(</mo><mi>A</mi><mo>+</mo><mi>B</mi><mo>−</mo><mi>C</mi><mostretchy="false">)</mo></mrow><annotationencoding="application/x−tex">Sin(B+C−A)+Sin(C+A−B)+Sin(A+B−C)</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mopen">(</span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">+</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7667em;vertical−align:−0.0833em;"></span><spanclass="mordmathnormal"style="margin−right:0.07153em;">C</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">−</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mordmathnormal">A</span><spanclass="mclose">)</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">+</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mopen">(</span><spanclass="mordmathnormal"style="margin−right:0.07153em;">C</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">+</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7667em;vertical−align:−0.0833em;"></span><spanclass="mordmathnormal">A</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">−</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mclose">)</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">+</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mopen">(</span><spanclass="mordmathnormal">A</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">+</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7667em;vertical−align:−0.0833em;"></span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">−</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mordmathnormal"style="margin−right:0.07153em;">C</span><spanclass="mclose">)</span></span></span></span>simplified?</strong>A:Theexpressionissimplifiedbyusingthesumanddifferenceformulasforsine,andthencombiningliketerms.</p><p><strong>Q:Whatisthefinalsimplifiedexpression?</strong>A:Thefinalsimplifiedexpressionis<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mimathvariant="normal">Sin</mi><mo></mo><mi>A</mi><mimathvariant="normal">Sin</mi><mo></mo><mi>B</mi><mimathvariant="normal">Sin</mi><mo></mo><mi>C</mi></mrow><annotationencoding="application/x−tex">SinASinBSinC</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6833em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal">A</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal"style="margin−right:0.07153em;">C</span></span></span></span>.</p><p><strong>Q:Howdoesthisexpressionrelatetotheoriginalequation?</strong>A:Theexpression<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mimathvariant="normal">Sin</mi><mo></mo><mi>A</mi><mimathvariant="normal">Sin</mi><mo></mo><mi>B</mi><mimathvariant="normal">Sin</mi><mo></mo><mi>C</mi></mrow><annotationencoding="application/x−tex">SinASinBSinC</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6833em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal">A</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal"style="margin−right:0.07153em;">C</span></span></span></span>isequalto<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>4</mn><mimathvariant="normal">Sin</mi><mo></mo><mi>A</mi><mimathvariant="normal">Sin</mi><mo></mo><mi>B</mi><mimathvariant="normal">Sin</mi><mo></mo><mi>C</mi></mrow><annotationencoding="application/x−tex">4SinASinBSinC</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6833em;"></span><spanclass="mord">4</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal">A</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal"style="margin−right:0.07153em;">C</span></span></span></span>,whichistheright−handsideoftheoriginalequation.</p><p><strong>Q:Whatisthesignificanceofthisproof?</strong>A:Thisproofdemonstratestheuseoftrigonometricidentitiesandalgebraicmanipulationstosimplifycomplexexpressionsandprovemathematicalstatements.</p><p><strong>Q:Canthisproofbeappliedtoothermathematicalproblems?</strong>A:Yes,thisproofcanbeappliedtoothermathematicalproblemsthatinvolvetrigonometricfunctionsandalgebraicmanipulations.</p><p><strong>Q:Whataresomepotentialapplicationsofthisproof?</strong>A:Somepotentialapplicationsofthisproofinclude:</p><ul><li>Solvingtrigonometricequationsandinequalities</li><li>Provingothermathematicalstatementsinvolvingtrigonometricfunctions</li><li>Developingnewmathematicaltechniquesandmethods</li></ul><h2><strong>Conclusion</strong></h2><p>Inthisarticle,wehaveexploredamathematicalprobleminvolvingtrigonometricfunctions.Wehaveusedthesumanddifferenceformulasforsinetosimplifytheexpression<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mimathvariant="normal">Sin</mi><mo></mo><mostretchy="false">(</mo><mi>B</mi><mo>+</mo><mi>C</mi><mo>−</mo><mi>A</mi><mostretchy="false">)</mo><mo>+</mo><mimathvariant="normal">Sin</mi><mo></mo><mostretchy="false">(</mo><mi>C</mi><mo>+</mo><mi>A</mi><mo>−</mo><mi>B</mi><mostretchy="false">)</mo><mo>+</mo><mimathvariant="normal">Sin</mi><mo></mo><mostretchy="false">(</mo><mi>A</mi><mo>+</mo><mi>B</mi><mo>−</mo><mi>C</mi><mostretchy="false">)</mo></mrow><annotationencoding="application/x−tex">Sin(B+C−A)+Sin(C+A−B)+Sin(A+B−C)</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mopen">(</span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">+</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7667em;vertical−align:−0.0833em;"></span><spanclass="mordmathnormal"style="margin−right:0.07153em;">C</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">−</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mordmathnormal">A</span><spanclass="mclose">)</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">+</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mopen">(</span><spanclass="mordmathnormal"style="margin−right:0.07153em;">C</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">+</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7667em;vertical−align:−0.0833em;"></span><spanclass="mordmathnormal">A</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">−</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mclose">)</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">+</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mopen">(</span><spanclass="mordmathnormal">A</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">+</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7667em;vertical−align:−0.0833em;"></span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">−</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mordmathnormal"style="margin−right:0.07153em;">C</span><spanclass="mclose">)</span></span></span></span>andprovedthatitisequalto<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>4</mn><mimathvariant="normal">Sin</mi><mo></mo><mi>A</mi><mimathvariant="normal">Sin</mi><mo></mo><mi>B</mi><mimathvariant="normal">Sin</mi><mo></mo><mi>C</mi></mrow><annotationencoding="application/x−tex">4SinASinBSinC</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6833em;"></span><spanclass="mord">4</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal">A</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal"style="margin−right:0.05017em;">B</span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mop"><spanclass="mordmathrm">Sin</span></span><spanclass="mspace"style="margin−right:0.1667em;"></span><spanclass="mordmathnormal"style="margin−right:0.07153em;">C</span></span></span></span>.Thisproofdemonstratestheuseoftrigonometricidentitiesandalgebraicmanipulationstosimplifycomplexexpressionsandprovemathematicalstatements.Wehopethatthisarticlehasprovidedausefulresourceforstudentsandmathematiciansinterestedintrigonometryandalgebra.</p>