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| 1. |
Cos(3π/4+x)-cos(3π/4-x)=-√2sinx |
| Answer» L.H.S. = Cos(3π/4+x)-cos(3π/4-x)= cos 3π/4 cos x - sin 3π/4 sin x - [cos 3π/4 cos x\xa0+ sin 3π/4 sin x]= cos 3π/4 cos x - sin 3π/4 sin x - cos 3π/4 cos x\xa0- sin 3π/4 sin x]= -2sin 3π/4 sin x= -2 x (1/√2) sin x= -√2sin x | |