Function of 2 variables calculation

A small bead moves on the surface defined by z = x^{2} + 2y^{2} + 3x + 2y - 4. The x and y coordinates at time t are determined by (x,y) = (cos t, sin t) . Determine the z ordinate of the bead when t=1. How do you do this, please can I have a walkthrough? :)

Re: Function of 2 variables calculation

We have x(t) = cos t, y(t) = sin t. Substitute t = 1 and evaluate x and y. Then substitute these x and y into the expression for z.

Re: Function of 2 variables calculation

Sorry, don't even know why I needed help with this! Got it - don't worry!

Re: Function of 2 variables calculation

I was kind of wondering that myself!