00:01
Okay, we want to find the slope of the tangent line, which is dy, dx.
00:05
So to find that, we'll have to do dy, d theta over dx, d theta.
00:13
Okay, and remember y is r sine theta, and x is r cosine theta.
00:22
So dyd theta would be the first times the derivative of the second plus the second times the derivative of the first, r prime.
00:33
And then the first times the derivative of the second plus the second times r prime, derivative of the first.
00:46
Okay, so d -y -d -x, r, which is the cosine of 2 -theta, times the cosine of theta, plus the sign of theta, times the derivative of the cosine of 2 theta, which would be minus 2, sine, 2, theta.
01:07
And then r, let's put the minus sign first, cosine 2 theta times sine theta plus cosine theta times minus 2 sine 2 theta.
01:21
So then dy, dx at theta equals 0 will be the cosine of 0 times the cosine of 0, plus the sign of zero, which is zero.
01:39
And then here, the cosine of zero times the sign of zero, that would be zero again, plus, oh, that'll be zero also...