`intsec^nxtanxdx,n!=0`

Explanation

`I=int sec^(n)x tan x dx`
`I=intsec^(n-1)x sec x tanx dx`
Let `sec x= t rArr sec x tan x dx=dt`
`therefore" "I=int l^(n-1)dt` ltbr. `=(t^(n))/(n)+c`
`=(sec^(n)x)/(n)+c`