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Grade 12Trigonometry

Prove that cos(A+B)cosC - cos(B+C)cosA = sinBsin(C-A)

Profile image of shubham
8 Years agoGrade 12
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2 Answers

Profile image of YASH AHUJA
8 Years ago
= (cosAcosB - sinAsinB)cosC - (cosBcosC - sinBsinC)cosA= cosAcosBcosC - sinAsinBcisC - cosAcosBcosC + sinBsinCcosA= sinBsinCcosA - sinBsinAcosC= sinB(sinCcosA - cosCsinA)= sinBsin (C- A)
Profile image of Shiva
6 Years ago
= (cosAcosB - sinAsinB)cosC - (cosBcosC - sinBsinC)cosA
= cosAcosBcosC - sinAsinBcisC - cosAcosBcosC + sinBsinCcosA
= sinBsinCcosA - sinBsinAcosC= sinB(sinCcosA - cosCsinA)
= sinBsin (C- A)

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