Question | Answer |
What is the Chain rule for partial derivatives? | dz/dt= (dz/dx)*(dx/dt)+(dz/dy)*(dy/dt) |
How do you find the domain of a multi-variable function? | Find any points at which f(x,y) is undefined and put it in the form x+y>0 |
What does the partial derivative of a function represent? | the slope of the tangent plane, and instantaneous rate of change. |
How do you find the best dimensions for a box? | write out what you know. xyz=32
Sub out the Z variable. Using this new information make an equation for the quantity that your trying to optimize. |
How do you find the tangent plane to a function? | Z=Z0+fx(X0,Y0)(X-X0)+fy(X0,Y0)(Y-Y0) |
How do you find the gradient vector? | del f(X0,Y0)=fx(X0,Y0)I + fy(X0,Y0)J |
How do you find the directional derivative? | del f . unit vector |
How do you find a unit vector? | A/|A| |
How do you find the local maxs and mins in higher dimensions? | Find the critical points, (fx=0,fy=0), find f''(x,y)if its negative then its concave down meaning there's a maximum value, if its positive then its concave up meaning there's a minimum value. |
How do you find D using the second order partial test?? | |fxx fxy|
|fxy fyy| |
How do you apply the second order partial test? | -if D>0 and fxx>0 then theres a local min@(X0,Y0)
-if D>0 and fxx<0 then theres a local max@(X0,Y0)
-if D<0 then theres no extreme value and its a saddle point. |