Find exact values of sin theta and cos theta

Question

Suppose the terminal side of angle θ lies in quadrant three on the line y = 5/6x. Find the exact values of sin θ and cos θ.

Answer 1

r(cos(theta)) = -5; r(sin(theta)) = -6; r = sqrt((-5)^2 + (-6)^2) = sqrt(25 + 36) = sqrt(61)

cos(theta) = -5/sqrt(61) = -5(sqrt(61))/61; sin(theta) = -6/sqrt(61) = -6(sqrt(61))/61