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Grade: 11 

                        
cos x + cos y = 0= sin x +sin y then cos 2x +cos 2y =?
3 years ago

Answers : (1)

Faiz
107 Points 
							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.....
3 years ago
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