# Really hard integrals?

1. Jan 1, 2016

### royjsky

I believe this uses multivariable calculus since I recall you must first prove the definite integral of the e^-x^2 which requires double integrals and a change of variables.

2. Jan 1, 2016

### royjsky

I think you need multivariable to do that.

3. Jan 17, 2016

### Corbeau

Here is a hard nut to crack. Been trying to solve it for a while, can't confirm it's actually solvable.

1/ ( x ( ln (x+1) -1 ) )

4. Feb 16, 2017

### suprabhe

x^2arctan(5x)

5. Mar 9, 2017

### Demystifier

Last edited by a moderator: May 8, 2017
6. Mar 9, 2017

### MAGNIBORO

$$\int_{0}^{\pi}\frac{cos(nx)-cos(na)}{cos(x)-cos(a)} dx$$

and

$$\int_{0}^{\infty }\frac{x}{e^{x}-1} dx$$

Last edited: Mar 9, 2017
7. Oct 13, 2017

### Suraj Pal

Try this.

8. Dec 26, 2017

### Ritam Dutta

it should come from common sense i think. seems the analytical method is gonna be just WOOW

9. Dec 27, 2017