a stands for alpha b stands for beta

If sin a= -8/17 and a is in the 4th quadrant angle, and tan b= 3/4 and 180degrees is less than or equal to b, and b is less than or equal to 270degrees find the values of each of the following:

a) cos a b) tan a c) sin b d) cos b e) cos(a+b) f) sin(a-b)

g) tan(b-a) h) sin2b i) tan2a j) cos2a k) sin a/2

l) tan b/2