Sin theta 78 cos 0 find cos 2 thetaSolutionsin theta 78 s

Sin theta = 7/8, cos > 0 find cos 2 theta

sin theta = 7/8

sin theta = perpendicular / hypotenuse

perpendicular = 7

hypotenuse = 8

base = sqrt (8^2 - 7^2) = sqrt 15

cos theta = base / hypotenuse = sqrt 15 / 8

cos2 theta = cos^2 theta - sin^2 theta

plugging the values of cos theta and sin theta

cos 2 theta = ( sqrt 15/8)^2 - (7/8)^2

cos 2 theta = 15/64 - 49/64 = -34/64