Answer
$(\cos\theta)^{2}$
Work Step by Step
For ease we express squares of trigonometric functions as following-
$(\cos\theta)^{2}$ = $\cos^{2}\theta$
This indicates we mean to square the number that is the cos of $\theta$.
or
$(\tan\theta)^{2}$ = $\tan^{2}\theta$
This indicates we mean to square the number that is the tan of $\theta$.
