Christopher Johnson Calculus III
Project – Matlab 3-‐D Surfaces 4/20/15
OBJECTIVE Use Matlab and knowledge of derivatives to map a 3-‐D surface and its tangent lines. METHOD 1) Given the following equation:
! !,! = −!!
2 − !! +258
at point P: (2,4,− !"
!)
Find partial derivatives with respect to x & y, which gives the slope in each respective direction. !! !,! = −! ; !! !,! = −2!
This gives the slopes in each direction. !! 2,4 = −2 ; !! 2,4 = −4
2) Use Matlab code to define variables (x,y) with their domain and range, solve
for function and its derivatives, equations for lines in x & y, create a for loop using the above equation, and finally use the plot and surf commands to create a 3-‐D surface of the function and its directional slopes in separate colors for visibility.
CONCLUSIONS Mapping a 3-‐D surface function and its tangent lines at a point using Matlab gives a powerful visual tool to understand how derivatives work with regards to a volume. The bounds can be easily changed, or different functions can be evaluated and graphed using similar code. This is what a 3-‐D graphing utility typically does for the user when it is given a function, it solves for the function at all the different points. By emphasizing the tangent lines, it is easier to understand how the surface is behaving at exactly that point in terms of its slope in x and y.