00:02
In this problem, we're going to convert to polar and we're going to integrate.
00:07
So let's get us a picture.
00:09
So first we have dx from y to the square root of 2y minus y squared.
00:14
So x equals y, which is this line, which we know is theta equals pi over four.
00:36
And then x equals square root of 2 y minus y squared.
00:42
So square both sides, add the y squared over.
00:49
So you get r squared equals 2r sine theta, or r equals 2 sine theta.
01:04
So in rectangular, it looks like this, starts at 0, goes to 2, 0, down to negative 2, 0.
01:15
So when you draw it in polar, starts here at 0.
01:19
By the time you get to pi over 2, you have to get to 2 in a positive way.
01:26
And then you have to get back to zero again.
01:30
Okay, so switching to polar, what's r doing? it's starting at r equals zero and going out to the edge of the blue circle, which is this...