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If A + B + C = pi, then what is cos(A + ...

If A + B + C = `pi`, then what is cos(A + B) + cos C equal to ?

A

0

B

2 cos C

C

cos C - sin C

D

2 sin C

Text Solution

Verified by Experts

The correct Answer is:
A
`A + B + C = pi`
`A + B = pi - C`
`cos(A+B)=cos(pi-C)`
`cos(A+B)=-cos C`
`or cos(A+B)+cos C = 0`
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