# Integral homework help

1. Nov 25, 2008

### Ed Aboud

1. The problem statement, all variables and given/known data

I'm trying to solve $$\int \frac{dy}{\sqrt{y^2 + C}}$$

2. Relevant equations

3. The attempt at a solution

Is it $$ln |y + \sqrt{y^2 + C^2} |$$

Or is it $$sinh^-^1$$ something.

Thanks.

2. Nov 25, 2008

### Dick

Re: Integral

It might be both, your first expression looks rather like sinh^(-1) to me as well. Why don't you try doing it? Put y=C*sinh(u) (assuming you mean y^2+C^2 in the integrand).

3. Nov 25, 2008

### Ed Aboud

Re: Integral

It turns out that its $$sinh^-^1 (\frac{y}{c})$$

Because my original differential equation was $$\frac{d^2y}{dt^2} - y = 0$$

Thanks!

4. Nov 25, 2008

### Dick

Re: Integral

arcsinh(y/C)=ln(y/C+sqrt(y^2/C^2+1)). That's the same as ln(y+sqrt(y^2+C^2)) up to a constant. They are both right.