Angle 0 is in quadrant II, and sin0 = 5/13. What is the value of cos0?

Answer 1

The triangle is 5, 12 and 13 in quadrant 2. SinQ is 5/13, so cos Q is -12/13. 5, 12 and 13 is a pythagorean triple like 3, 4 and 5. 5^2 +12^2 = 25 +144 = 169 = 13^2. In quadrant 2 cos is negative.