# How do you know when it's time for Trignometric Subsitution ?

1. Oct 22, 2006

### jkh4

How do you know when it's time for "Trignometric Subsitution"?

How do you know when it's time for "Trignometric Subsitution"?

2. Oct 22, 2006

You should be more specific about that question.

3. Oct 27, 2006

### ice109

it an integration technique. it should always "work". sometimes it just makes things easier.

4. Oct 27, 2006

### arildno

Whenever a trigonometric substitution simplifies your integrand significantly.

5. Oct 27, 2006

### marcmtlca

Usually when you see something like $$\frac{1}{\sqrt{1+x^2}}$$ or $$\frac{1}{\sqrt{1-x^2}}$$ or anything similar then you can think about using a trig sub. I usually think of trig sub when I see somethign that looks like the derivative of an inverse trig functions. (you should memorize those). But there are definately many cases where a trig sub could be used...

6. Oct 27, 2006

### Office_Shredder

Staff Emeritus
basically whenever you see a 1 and an x2, you can do some sort of trig or hyperbolic trig substitution to make things easier. Of course, if you're not sure, try solving it without the substitution, and only if you get stuck should you go for it (since if it's not useful, it can be a real pain in the ass trying to figure that out).