CPM Homework Help : PC3 Problem 11-147

Given $\cos(A) = \frac { 5 } { 13 }$ where $0 < A <\frac { \pi } { 2 }$ , evaluate $\csc(A)$ and $\cos(2A)$ .

Step 1:

Sketch a right triangle for the given situation and then determine the length of the missing leg.

Step 2:

$\csc(A) = \frac{1}{\sin(A)}$

Step 3:

$\cos(2A) = \cos^2 (A)- \sin^2(A)$