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cos x + cos y = 0= sin x +sin y then cos 2x +cos 2y =?

cos x + cos y = 0= sin x +sin y then
cos 2x +cos 2y =?
 

Grade:11

1 Answers

Faiz
107 Points
7 years ago
cosx + cosy = 0 ......1sinx + siny = 0 ......2Squaring both the equations and subtracting 2 from 1....we get:-> cos²x - sin²x + cos²y - sin²y + 2(cosxcosy - sinxsiny) = 0.....-> cos 2x + cos 2x + 2cos(x+y) = 0-> cos 2x + cos 2y = -2cos(x+y)....ans.....

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