00:01
So for this problem, we just need to recall that d, y, d, d, x, the slope of y with respect to x, when you have parametric equations, you can just do the ratio of dydt to dx dt.
00:17
Okay? and what is that? well, we need to take some derivatives.
00:22
So dydt, we need some product rule here.
00:26
So this is e to the t sine t plus e to the t.
00:33
Cosine t over d x d t which is e to the t cosine minus e to the t sine t okay and so to have a zero slope i need d y d t the top to be zero so let's set that equal to zero so if e to the t plus a sine t e to the t sine t plus i'm gonna go ahead and factor out the e to the t okay we want this to be equal to zero.
01:18
Well, e to the t is never zero, so just get rid of that.
01:20
So we want points where sine t is equal to negative cosine t between zero and two pi.
01:26
Sorry, my dog is currently whining for attention.
01:30
She's cute, but we're doing math right now.
01:33
All right, so that's cool.
01:36
So let's think about where does this happen on the unit circle? we want the y coordinate to be the negative of the x coordinate.
01:44
So their values should be the same, but the signs, should be different.
01:48
That happens here and here...