Find ( - 7 2 ) = ?

Answer: Option D

$$\begin{array}{rl}& \cos \left(-\frac{7\pi }{2}\right)\\ & =\cos 7\times \frac{180}{2}\\ & =\cos 630\\ & =\cos \left(2\times 360-90\right)\\ & =\cos 90\\ & =0\end{array}$$