साबित करें कि
`tan 4x = ( 4 tanx ( 1- tan^(2) x))/( 1- 6 tan^(2) x + tan ^(4) x )`

Explanation

L.H.S. `tan4x = tan 2 (2x) = ( 2 tan2x)/(1-tan^(2) 2x)`
`= ( 2 (2tanx)/(1-tan^(2)x))/(1-((2 tanx )/(1-tan^(2)x))^(2))= (4tanx)/(1-tan^(2)x)xx((1-tan^(2)x)^(2))/((1-tan^(2)x(1-tan^(2)x^(2))^(2))-4 tan^(2)x)`
`= (4 tan ( 1-tan^(2)x))/( 1-2 tan^(2)x + tan^(4)x -4tan^(2)x)`
`= ( 4 tan(1-tan^(2)x ))/(1-6tan^(2) +tan^(4)x) = R.H.S.`