00:01
So i have the function, cosine of x squared, plus y squared, and i am asked to find the quadratic and cubic approximations of these using taylor's formula.
00:11
And i'm going to do this at the origin.
00:14
So to start with the quadratic, that means i need my partial derivatives up to 2.
00:19
So find my partial derivative with respect to x.
00:22
Using chain rule here, so cosigns become negative sign.
00:26
Derivative the inside is 2x, so i get minus 2x.
00:29
Sine of x squared plus y squared doing the same thing with y i just get the negative 2y um sign of x squared plus y squared so taking the second partial derivative with respect to x here i'm going to have to use my product rule so i'm going to have first taking the derivative of the first part i have negative 2 sign x squared plus y squared derivative of the sign, i end up with minus 4x squared, cosine, x squared plus y squared.
01:27
And then doing the same thing, but now with respect to y, i'm not using product rule anymore, so i just end up with a minus 4xy cosine of x squared plus y squared...