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Solve the equations: cos theta + cos 3...

Solve the equations:
cos `theta + cos 3theta = 2 cos 2theta`

Text Solution

Verified by Experts

We have `cos theta+ cos 3 theta- 2 cos 2 theta=0`
or `2 cos 2 theta cos theta-2 cos 2 theta=0`
or `2 cos 2 theta( cos theta-1) =0`
or `cos 2 theta=0 or cos theta-1 =0`
`rArr 2 theta=(2n+1) pi/2, n in Z or theta=2 mpi, m in Z`
or `theta=(2n+1) pi/4, n in Z or theta =2mpi, m in Z`
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