# Integral, from 0 to 1, of dx/root(1-x^2)

1. Dec 3, 2014

### leo255

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

Integral, from 0 to 1, of dx/root(1-x^2)

2. Relevant equations

d/dx of arcsin = 1/root(1-x^2)

3. The attempt at a solution

Since d/dx of arcsin = 1/root(1-x^2), we have that the integral, from 0 to 1, of dx/root(1-x^2) equals to arcsin, from 0 to 1.

arcsin(1) - arcsin(0) = arcsin(1). I know I'm missing something here. What did I do wrong?

2. Dec 3, 2014

### Zondrina

Nothing is wrong.

3. Dec 3, 2014

### ehild

What is arcsin(1)?

4. Dec 3, 2014

### leo255

arcsin(1) is pi/2. I asked someone in my class about this, and he said that I should be taking the limit, as b (or whatever other variable) approaches 1, from the left-hand side. Can you guys confirm if this is something that should be done for this problem?

5. Dec 3, 2014

### Staff: Mentor

Yes, this should be done. The integrand is undefined at x = 1, so the Fund. Thm. of Calculus doesn't apply. You can get around this by evaluating this limit:
$$\lim_{b \to 1^-}\int_0^b \frac{dx}{\sqrt{1 - x^2}}$$