00:01
Right, so for here we have f of x, y is equal to xy over x squared plus y squared.
00:09
The domain here is all points except for zero, zero, because the denominator is going to be zero there.
00:17
So the domain is all points except 0, 0.
00:25
Now we can use polar form, so where x is equal to our cosine of theta, and y is equal to r times sine of theta.
00:36
So then we have f of x, y is equal to, so r squared, cosine theta, sine theta over r squared.
00:49
So we have f of xy is equal to cosine theta, sine theta, which is equal to one -half sine of 2 theta.
01:04
So the value here depends only on the direction theta, not the distance from the origin...