Hello! I have two problems I need help on.

use sum or difference to find the exact value of each trigonometric function.

cot 113pi/12

I know this equals= 4(360)+255

and 255 is 210+45

So I did

cot(210)+cot(45)/(1-cot(210)(cot45)

Which gives me -3.739 But I am quite sure this is wrong.(Giggle)

my second problem is

cos(x+y)= tanx(5/3) and sin y=1/3

I am quite confused on this one

Can anyone help me with these problems?