Section 12.3

Sketch a contour diagram for the function with at least four labeled contours .  
Describe in words the contours and how they are spaced.

f (x, y) = (1/2) ((x^2) + (y^2))

Section 13.4

Let A = (2, -1, -1), 
    B = (3, 1, 0), 
    and C = (1, 2, 1) . 
(a) 
        Find an equation for the plane that passes through these three points . 
(b) 
        Find the area of the triangle determined by these three points .  




Xiaoqi Cui