trig
posted by kristen on .
establish the identity:
cot(AB)= cotAcotB+1/cotBcotA
thanks for any help at all

Is the final term
1/(cotBcotA) or
(1/cotB)cotA ??
Is the numerator term (cotA cotB +1) or 1 ?
When you write equations like that, we can't tell what you mean.
I suggest you start with the identities for cos (AB) and sin (AB) and take the ratio of the two. 
cos(a+b)/sin(a+b)=
cosacosb+sinasinb/sinacosbcosasinb
multiplying and dividing by sinasins then it becomes
cotacotb+1/cotbcota