Posted by **kristen** on Wednesday, July 16, 2008 at 6:35pm.

establish the identity:

cot(A-B)= cotAcotB+1/cotB-cotA

thanks for any help at all

- trig -
**drwls**, Wednesday, July 16, 2008 at 6:48pm
Is the final term

1/(cotB-cotA) 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 (A-B) and sin (A-B) and take the ratio of the two.

- trig -
**Anonymous**, Saturday, May 11, 2013 at 12:02pm
cos(a+b)/sin(a+b)=

cosacosb+sinasinb/sinacosb-cosasinb

multiplying and dividing by sinasins then it becomes

cotacotb+1/cotb-cota

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