Trig Substitution

**x5pyd3rx** · April 20th 2010, 05:45 PM

The problem us integrate : $\frac{1}{x \sqrt{x^2+25}}dx$

I worked it out to here
$<br /> <br /> <br /> \frac{5secT}{5tanT} dT$

1. Is this right so far and 2. Im a little confused on how to proceed from there.

**Deadstar** · April 20th 2010, 05:57 PM

Well, ASSUMING what you did up to there was right then use...

$\sec(x) = \frac{1}{\cos(x)}$

and

$\tan(x) = \frac{\sin(x)}{\cos(x)}$

**TKHunny** · April 20th 2010, 06:01 PM

Good start. Extra factor of 5 in the numerator.

**x5pyd3rx** · April 20th 2010, 06:18 PM

Thats kind of what i thought so it should be $\frac{secT}{5tanT}dT$

**Deadstar** · April 21st 2010, 03:22 AM

Originally Posted by x5pyd3rx

Thats kind of what i thought so it should be $\frac{secT}{5tanT}dT$

No the 5's cancel. 5/5 = 1...

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