I suspect you mean
tan((m + n)/2)
on the RHS
Verify the Identity
(sin m +sin n)/ (cos m + cos n) = tan(m + n/2)
3 answers
yes i do.
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)
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)