Engineering Board Exam Reviewer · Vector Calculus: Gradient, Divergence, and Curl · medium

Find the directional derivative of =x2+yz at (1,2,1) in the direction of i+2 j+2 k.

1. 8
2. 2.67
3. 3
4. 1.33

Answer

B. 2.67

Solution

=2x, i+z, j+y, k=2 i+ j+2 k at (1,2,1). The unit direction is i+2 j+2 k/3. So D u =2+2+4/3= 83 2.67.

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