You are standing at the point (1,1,3) on the hill whose equation is given by z =
ID: 2968619 • Letter: Y
Question
You are standing at the point (1,1,3) on the hill whose equation is given by z = 5y - x^2 - y^2.
(a) If you choose to climb in the direction of steepest ascent, what is your initial rate of ascent relative to the horizontal distance?
The answer for (a) I think is the gradient vector of z. Is this right? If I'm right the answer is grad z = -2i + 3j. Please let me know if I'm wrong.
(b) If you decide to go straight northwest, will you be ascending or descending? At what rate?
So what I think is that north is + x direction and west is - y direction, So I think it is ascending.
The rate is the dot product of grad Z and unit vector of NW, so i think it is (5/sqrt{2}) . Please let me know if I'm wrong.
(c) If you decide to maintain your altitude, in what directions can you go?
I have no idea in this question.
Explanation / Answer
f(x) = -x^2 +5y-y^2-z
steepest ascent direction :
f'x. i + f'y. j+ f'z k
f'x = -2x = -2
f'y = 5-2y = 3
f'z = -1
steepest ascent direction = -2i+3j-k
(b
)
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