Let sinx = 2/3 , with x in quadrant II and cosy = 3/5, with y in quadrant IV. Find tan(2x)
Find sin(y/2)
Find cos(x -y)
find sin(x +y)
sinx = 2/3
cosx = -√5/3
cosy = 3/5
siny = -4/5
Now just use your formulas. For example,
cos(x-y) = cosx cosy + sinx siny = -√5/3 * 3/5 + 2/3 * -4/5 = -(3√5+8)/15