1.

What `int sec x^(@) dx` is equal to ?A. `log (sec x^(@) + tan x^(@)) + c`B. `(pi log tan ((pi)/(4) + (pi)/(2)))/(180^(@)) + c`C. `(180^(@) log tan ((pi)/(4) + (x)/(2)))/(pi) + c`D. `(180^(@) log tan ((pi)/(4) + (x)/(360^(@))))/(pi) + c`

Answer» Correct Answer - A
`int sec x^(@).dx = int (sec x^(@).(sec x^(@) + tan x^(@)))/(sec x^(@) + tan x^(@)) .dx`
Let `u = sec x^(@) + tan x^(@)`
`rArr (du)/(dx) = sec x^(@) + tan x^(@) + sec^(2) x^(@)`
`rArr du = (sec x^(@) xx tan x^(@) + sec^(2) x^(@)) .dx`
`:. in (sec x^(@).(sec x^(@) + tan x^(@)))/(sec x^(@) + tan x^(@)) dx`
`= int (sec^(2)x^(@) + sec x^(@) tan x^(@))/(sec x^(@) + tan x^(@)).dx`
`= int (du)/(u) = log (u) + C = log (sec x^(@) + tan x^(@)) + C`


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