# Find the length of the cureve

1. Dec 1, 2012

### manal950

http://store3.up-00.com/Nov12/Mna64759.jpg [Broken]

http://store3.up-00.com/Nov12/tZz64759.jpg [Broken]

Last edited by a moderator: May 6, 2017
2. Dec 1, 2012

### SteamKing

Staff Emeritus
1. On page 1, the integral for L is taken w.r.t. the variable t, so you are missing 'dt'.
2. On page 1, the first eqn. under the integral for L is not dx/dt. However, the expression below that appears to be OK.
3. On page 2 at the bottom, you have not integrated 8t correctly w.r.t. the variable 't'. If you integrals don't have a d(something) somewhere, you don't have a complete expression.

3. Dec 1, 2012

### manal950

thanks so much

so the last step for L is correct except integration of 8t

4. Dec 1, 2012

### SteamKing

Staff Emeritus
it appears so.

5. Dec 2, 2012

### manal950

Is the final answer is (pi^2 )

6. Dec 2, 2012

### Staff: Mentor

Yes.

As mentioned at least three other times by other people, your integrals need the differential, dt or dx or whatever it happens to be. If you persist in leaving them out, you will get the wrong answer when you attempt to evaluate integrals using techniques such as trig substitution and integration by parts.