Evaluate : `intsec^4 x tan x dx.`

Explanation

We have given,

`intsec^4 x tan x dx.`

Let

`I =int sec ^{4} x cdot tan x cdot d x `

`I=int sec ^{2} x cdot sec ^{2} x cdot tan x cdot d x `

`I=int(1+tan ^{2} x) tan x cdot sec ^{2} x cdot d x`

Since[`1+tan ^{2} x=sec ^{2} x`]

Let `tan x=t quad implies sec ^{2} x cdot d x=d t`

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