The number of solution the equation `cos(theta).cos(pitheta)=1` has 0 (b) 1 (c) 4 (d) 2

Explanation

`cos theta * cos(pi theta) = 1`

We know value of `cos theta` can not be greater than `1`.

So, only two below cases are possible for the given solution.

Case 1: When `cos theta = 1 and cos(pitheta) = 1`

`=>theta = 2npi and pitheta = 2npi`

`=>theta = 2npi and theta = 2n`

So, only common solution is, when `n = 0`, then `theta = 0` in this case.

Case 2: When `cos theta = -1 and cos(pitheta) = -1`

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