using the identity $\displaystyle (sec^2 X = 1+tan^2 X)$ find a reduction formula for the integral $\displaystyle ln=\int tan^n X dx, $ where n is greater than or equal to 2

hence evaluate $\displaystyle \int tan^4 X dx $ from 0 to pie/4 ( cant really type this in the mathematical terms.

ok to express this in reduction form i made

$\displaystyle tan^2 X = sec^2X-1$ (for the identity)

then substituted it in the expression $\displaystyle ln=\int sec^2X -1 $$\displaystyle dx$

did i do it right? and if so how would that help me to evaluate the integral.