Find the exact value of each of the following using reference angles.
a)sin 225degrees
b) cot 120degrees
sin 225 ---- third quad , sine is +
= -sin45 ---- 225-180 = 45
= -1/√2 or -√2/2
cot 120 ---- quad II, tan and cot are -
= -cot 60 ---- 180-120 = 60
= -1/√3 or -√3/3