Question 797527
If cos(a)=8/17 and 270° < a < 360°, then sin(a) equals?
reference angle (a) is in quadrant IV where cos>0 and sin<0
sin(a)=-&#8730;(1-cos^2(a))=-&#8730;(1-(8/17)^2)=-&#8730;(1-(64/289)=-&#8730;(225/289)=-15/17