Question

In 14 and 15, tan y = k. Evaluate.
14. tan(–y) 15. tan(180º – y)

Answer 1

Because sine, cosine, and tangent are functions (trig functions), they can be defined as even or odd functions as well. Sine and tangent are both odd functions, and cosine is an even function. In other words, sin(–x) = –sin x.

( http://www.dummies.com/how-to/content/how-to-simplify-an-expression-using-evenodd-identi.html)

The tangent is an odd function.

tan(-y) = - tan(y)