Question

Question no. 15,. cos2theta-sin2theta=tan2¤
Prove that costheta=1/√2costheta

Answer 1

Answer:

cos-sin =√2 sin

squaring both sides

(cos-sin) ²=(√2sin) ²

cos²+sin²-2cossin =2sin²

cos²=2sin²-sin²+2 cos sin

cos²=sin²+2cos sin

Adding cos both sides

cos²+cos²=sin²+2cos sin +cos²

2cos²=(sin+cos) ²

√(2cos²) = sin +cos

√2 cos = cos +sin

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