Tan65°-tan25°=2tan40° prove!

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