1.

Ecaluate the following: (i) `int(sec^(2)x)/(3+tanx)dx " (ii) " int(e^(x)-e^(-x))/(e^(x)+e^(-x))dx` (iii) `int(1-tanx)/(1+tanx)dx " (iv) " int(1)/(1+e^(-x))dx`

Answer» (i) `int(sec^(2)x)/(3+tanx)dx=int((d)/(dx)(3+tanx))/(3+tanx)dx`
`=log|3+tanx|+C`
(ii) `int(e^(x)-e^(-x))/(e^(x)+e^(-x))dx=int((d)/(dx)(e^(x)+e^(-x)))/(e^(x)+e^(-x))dx`
`=log_(e)(e^(x)+e^(-x))+C`
(iii) `int(1-tanx)/(1+tanx)dx =int(cosx-sinx)/(cosx+sinx)dx`
`=int((d)/(dx)(cosx+sinx))/(cosx+sinx)dx`
`=log_(e)|cosx+sinx|+C`
(iv) `int(1)/(1+e^(-x))dx=int(e^(x))/(e^(x)+1)dx`
`=int((d)/(dx)(e^(x)+1))/(e^(x)+1)dx`
`=log_(e)(1+e^(x))+C`


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