Question

tan70^o=2tan50^o+tan20^o prove this?

Answer 1

used this formula :
\(tan (A-B)=\frac{tanA-tanB}{1+tanAtanB}\)

Answer 2

tan(70-20)=tan50

\(\frac{(tan70-tan20)}{(1+tan20 tan70)}\) =tan50

tan20 tan70=cot70 tan70=1

(tan70-tan20)/2=tan50

tan70-tan20=2tan50

tan70=tan20+2tan50