Given,

To find the value of

[using the formula cos 2x = 2cos² x – 1]

[using the formula cos 2x = 2cos² x –1, here 2x = θ so x = ]

As given, now by dividing the whole inequation with 2 we get, .

This clearly state that lies in the 1^st quadrant and between 45° and 90°.

So