1. ## Arc Length!!

Show that the circumference of the unit circle is 2 *integral from -1 to 1 of 1/sqrt(1-x^2)

hint: use the equation x^2+y^2=1 and the arc length formula

I simplified my answer down to the integral from -1 to 1 of 1/sqrt(1-x^2) but how do i get it to be two times the whole thing?

2. ## Re: Arc Length!!

You need to double it since you are only using one half (probably the top or positive root).

3. ## Re: Arc Length!!

this is my work for the problem, where am i using only one half of the square root? i dont really get that. but i would need to write that in my work instead of just magically getting a 2 there at the end! thank you for your help!

4. ## Re: Arc Length!!

You third step, where you take the positive root of y...this represents only the top half of the circle.

Thank you!!