Date: Mar 11, 2013 4:39 PM
Author: Christopher Cargill
Subject: ACT Math Question

I am having some difficulty with the following ACT practice problem:

For X, an angle whose measure is between 270° and 360°, cosX=5/13. Which of the following equals tanX?
A. -5/12
B. -5/13
C. 5/13
D. 5/12
E. 12/13

The book I am using provides the answer and an explanation, but the explanation uses process of elimination to find the answer without actually describing a method of solving the problem. I would like to understand how to actually find the answer. Can someone lend a helping hand?