In the following problem:

solve:

Cos(tan

^{-1}x) = Sin[cot

^{-1}(3/4)]

In the above said problem, I proceeded

sin[(Pi/2) - tan

^{-1}x] = Sin[cot

^{-1}(3/4)]

(Pi/2) - tan

^{-1}x = cot

^{-1}(3/4)

Cot

^{-1}x = cot

^{-1}(3/4)

x = 3/4

However, they have given x = + 3/4 or - 3/4

How to identify it has two answers?

How to find the second answer.

Kindly enlighten me.

with warm regards,

Aranga