Question

Suppose cos(O) = 5/13, Quadrant I. Find sin(O).

A:13/12
B:12/13
C:13/5
D:5/12

Answer 1

B. 12/13.

Explanation:

Using the identity sin^2 O + cos^2 O = 1:

sin^2 O = 1 - cos^2 O

sin^2 O = 1 - (5/13)^2

= 1 - 25/169

= 169/169 - 25/169

= 144/169

So sin O = √(144/169)

= 12/13.