Question

Tan65°-tan25°=2tan40° prove !!!

Answer 1

tan65 - tan40 = tan 25 + tan 40 .

using tanA - tan B =sin(A - B)/cosAcosB and tanA + tan B

= sin( A + B)/cosAcosB

= we get :: to prove sin 25/ cos65

= sin65 / cos25 sin 25 = cos (90 - 25)

= cos 65 and sin 65

= cos (90 - 65)

= cos 25

-Leah