Question

Prove that =
Cos 7x + cos 5x
sin 7x + sin 5x
=cot x​

Answer 1

Step-by-step explanation:

LHS=(co7x+cos5x)/(sin7x+sin5x)

=2cos[(7x+5x)/2]cos[(5x-7x)/2]/{sin[(7x+5x/2)]cos[(7x-5x)/2]}

=(cos6xcosx)/(sin6xcosx)

=cosx/sinx

=cotx

LHS=RHS

hence proved