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What is the value of cos(90 - B)sin(C - A) + sin(90 + A)cos(B + C) - sin(90 - C)cos(A + B)?

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What is the value of cos(90 - B)sin(C - A) + sin(90 + A)cos(B + C) - sin(90 - C)cos(A + B)?
  • A1
  • Bsin( A + B - C)
  • Ccos( B + C - A)
  • D0
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Discussion 1

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CCommunity
cos(90 - B)sin(C - A) + sin(90 + A)cos(B + C) - sin(90 - C)cos(A + B)

⇒ sinBsin(C - A) + cosAcos(B + C) - cosCcos(A + B)

⇒ sinB(sinCcosA - cosCsinA) + cosA(cosBcosC - sinBsinC) - cosC(cosAcosB - sinAsinB)

⇒ sinBsinCcosA - sinBcosCsinA + cosAcosBcosC - cosAsinBsinC - cosCcosAcosB + cosCsinAsinB = 0