# Evaluating $\tan(\frac{\pi}{2}-y)$

I'm trying to evaluate

$$\tan(\frac{\pi}{2}-y)$$

The answer I get is $-\cot(y)$ but the answers I have say it's $\cot(y)$

I'm not sure why it's not negative

Thanks

• If you show your work we may be able to point out the mistake. The correct answer is $cot(y)$; this identity is one of the "cofunction identities". – Spencer Aug 14 '16 at 5:44

Hint: Try drawing a right triangle with the other $2$ angles being $y, \frac{\pi}{2} - y$. You can then visually see that tangent of one angle is cotangent of the other. As @Spencer said if you want to know where you made a mistake please let us know what you've tried.