How do you evaluate the integral int sqrt(e^x+1)ex+1?

1 Answer
May 23, 2018

Use the substitution sqrt(e^x+1)=uex+1=u.

Explanation:

Let

I=intsqrt(e^x+1)dxI=ex+1dx

Apply the substitution sqrt(e^x+1)=uex+1=u:

I=2int(u^2)/(u^2-1)duI=2u2u21du

Rearrange:

I=2int(1+1/(u^2-1))duI=2(1+1u21)du

Factorize the denominator:

I=2int(1+1/((u-1)(u+1)))duI=2(1+1(u1)(u+1))du

Apply partial fraction decomposition:

I=int(2+1/(u-1)-1/(u+1))duI=(2+1u11u+1)du

Integrate term by term:

I=2u+ln|u-1|-ln|u+1|+CI=2u+ln|u1|ln|u+1|+C

Reverse the substitution:

I=2sqrt(e^x+1)+ln|(sqrt(e^x+1)-1)/(sqrt(e^x+1)+1)|+CI=2ex+1+lnex+11ex+1+1+C