# Determining signs of partial derivatives

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• May 20th 2009, 09:36 AM
Kaitosan
Determining signs of partial derivatives
How do you determine the slope signs by just looking at 3D graphs? (Wondering)
• May 20th 2009, 08:34 PM
Scott H
We look at the slope in the positive direction of the $x$- and $y$-axes. If the surface is curving down, the slope is negative, if up, the slope is positive.

When you learn about directional derivatives, you will be able to calculate the slope in any direction, not just the positive direction of the $x$- and $y$-axes.