trigonometric equations

cos x-sin 3x=cos2x
find the general solution for x.

2 Answers

466
Himanshu Giria ·

X=2nπ3
Or X=2nπ3 + π/6

1357
Manish Shankar ·

cosx-cos2x=sin3x

2sin(x/2)sin(3x/2)=sin3x

2sin(x/2)sin(3x/2)-sin3x=0

2sin(x/2)sin(3x/2)-2sin(3x/2)cos(3x/2)=0

2sin(3x/2)[sin(x/2)-cos(3x/2)]=0

proceed from here

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