The angle θ lies in Quadrant II .
sinθ=34
What is cosθ ?
sin2θ + cos2θ = 1
(3/4)2 + cos2θ = 1
cos2θ = 1 - (3/4)2
cos2θ = 1 - 9/16
cos2θ = 7/16
cos θ = ±√[ 7/16 ]
cos θ = ±√7 / 4
Since θ is in Quadrant II , cos θ is negative.
cos θ = - √7 / 4
