Question 824976
If sin(theta) = 4/5, what is the value of cos(theta) in quadrant 1? 



sin^2(theta) + cos^2(theta) = 1


(4/5)^2 + cos^2(theta) = 1


16/25 + cos^2(theta) = 1


cos^2(theta) = 1 - 16/25


cos^2(theta) = 25/25 - 16/25


cos^2(theta) = (25 - 16)25


cos^2(theta) = 9/25


cos(theta) = sqrt(9/25) ... we are in quadrant I, so cos(theta) > 0


cos(theta) = 3/5