00:01
So for question 18, we are given the equation of the sphere, which is x squared plus c squared equals four.
00:08
And we want to find the point on the sphere that is farthest from the point 1, negative 1, 1.
00:16
So we're trying to maximize distance here.
00:18
So that means my f is going to be my distance formula.
00:24
I know that i want it to be farthest from the point 1, negative 1, 1.
00:28
So i'm going to plug that point into my distance formula and have it be the space.
00:32
Of it just so i don't have to deal with a square root.
00:34
So i'll have x minus one squared plus y plus one squared plus z minus one squared.
00:44
And then i'm given the restraint of the sphere.
00:49
So that's going to be my g that i'm going to be using from equation one.
00:54
And so i want to set that equal to zero.
00:56
So i have x squared plus y squared plus z squared minus four is equal to zero.
01:06
So i want to find the point that is furthest away from the point on this sphere that's furthest away from this point.
01:15
So do that, i am going to find the gradient of f and set equal to lambda times the gradient of g...