00:01
Okay, so for this problem, we have w equals sign of x, y, z.
00:09
I'm given that x equals 1 minus 3t, y equals e to the 1 minus t, and that z equals 4t.
00:21
So what we're asked to do is find w, dw over dt.
00:28
So now if we notice, w has x, y, and z, but no t.
00:32
So we're going to have to use chain rule.
00:35
So d w over d x d x over d t and then d w over d y d y over d y over d t d w over d z d z over d t okay so what i want to do is go back here and find d w over d x and so i know that the derivative of sign is going to be so, cosine, whoops, i want to scoot over just a little bit, x, y, z, then plus the derivative of x, y, z in terms of x, so it's going to be y z, and then this in terms of y, so again, it's going to be cosine, x, y, z, and then this one in terms of y, this will be, make this x, z.
01:38
Let's get down just a little bit, and then d w in terms of d z.
01:43
So we've got cosine of x, y, z.
01:47
And since we're taking this in terms of z, z, and since we're taking this in terms of z, this would be xy...