Posted by **Steve** on Saturday, October 24, 2009 at 3:56pm.

Verify the Identity

(sin m +sin n)/ (cos m + cos n) = tan(m + n/2)

- Trig -
**jim**, Saturday, October 24, 2009 at 5:50pm
I suspect you mean

tan((m + n)/2)

on the RHS

- Trig -
**Steve**, Saturday, October 24, 2009 at 11:28pm
yes i do.

- Trig -
**Arya**, Tuesday, December 1, 2009 at 5:07am
Use Lemma

sin m + sin n = 2sin(m+n/2)cos(m-n/2)

cos m + cos n = 2cos(m+n/2)cos(m-n/2)

We get

(sin m +sin n)/cos m + cos n) = sin(m+n/2)/cos(m+n/2) = tan m+n/2)

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