سیگما

`int (x)/(x^2-7x+13)dx`
`1/2 int (2x-7+7)/(x^2-7x+13)dx`
`1/2(int (2x-7)/(x^2-7x+13) dx+ 7 int 1/(x^2-7x+13) dx)`
`1/2ln(x^2-7x+13)+7/2int(dx)/((x-7/2)^2+(sqrt(3)/2)^2)`
`1/2ln(x^2-7x+13)+7/sqrt(3)arctan((x-7/2)/(sqrt(3)/2))`

`int (dx)/(x^2+2x+5)`
`int (dx)/((x+1)^2+2^2)`
`x+1=u , du=dx`
`int (du)/(u^2+2^2)`
1`1/2arctan((x+1)/2)`