# Integration of 1/x^2 sqrt(16-x) with substitution

1. Jan 22, 2006

### teng125

my question is integra 1 / x^2 sqr root(16-x^2)
i use x = 4 sin y
then i got to integrate 1/16 times [1/(sin y)^2] in which i got stuck.pls help.....how do i continue from there as i not sure ow to integra 1/(siny^2

2. Jan 22, 2006

### HallsofIvy

Staff Emeritus
$\frac{1}{sin^2y}= csc^2y$- you should know the integral for that. What is the derivative of cot y?

(Sorry- I had left out a "}")

Last edited: Jan 23, 2006
3. Jan 22, 2006

### Jameson

Since I can't see Halls' Latex image, he was saying that $$\int \csc^2(y)dy$$ is very simple, noting that what the derivative of cot(y) is.

4. Jan 22, 2006

### benorin

Ivy's image is: $$\frac{1}{sin^2y}= csc^2y$$