trigonometry
posted by kiko on .
given that sin alpha/2 = 2/3, and that alpha/2 is in quadrant II, determine the exact values of all trig functions for alpha.

let alpha/2 = A/2
sin A/2 = 2/3
then cos A/2 = √5/3
sin A = 2(sin A/2)(cos A/2) = 2(2/3)(√5/3) = 4√5/9
make a sketch,
opposite = 4√5, hypotenuse = 9
adj^2 + 80 = 81
adj = 1
sin alpha = 4√5/9
cos alpha= 1/9
tan alpha = 4√5
I am sure you can find the three reciprocal values