# Integral involving square root -need help

#### winbacker

1. Homework Statement

integrate sqrt(1-x^-2/3)^1/2.

2. Homework Equations

3. The Attempt at a Solution

The only thing I can think of is u substitution with u = 1 - x^-2/3. Obviously this cannot work because du differs by more than just a constant.

I guess I need to somehow factor this equation but I do not know how. I think I can pull out an x^1/3 or something but I'm not sure. Any help would be appreciated.

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#### maze

Whenever you see stuff like that in the square root, always think "Trig Substitution"!

Hint: 1-sin(x)^2 = cos(x)^2.

#### statdad

Homework Helper
Do you mean

$$\sqrt{1-x^{-2/3}}$$

or do you mean (as you've written)
$$\sqrt{(1-x^{-2/3})^{1/2}}$$

the first one

#### Mark44

Mentor
Whenever you see stuff like that in the square root, always think "Trig Substitution"!

Hint: 1-sin(x)^2 = cos(x)^2.
I'm not sure that trig substitution is the way to go in this problem. Trig substitution is a viable alternative for integrals that involve
$$\sqrt{a^2 + x^2}$$
$$\sqrt{a^2 - x^2}$$
$$\sqrt{x^2 - a^2}$$

Maybe it can be made to work in the OP's problem, but I don't see it.

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