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kingwinner
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http://www.geocities.com/asdfasdf23135/advcal4.JPG
Let f(x,y)=depth.
What I've seen in the model solutions is that they used the estimate that
the partial dervaitve of f with respect to x evaluate at (0,0) is equal to [f(100,0) - f(0,0)] / 100 = 1/4,
& the partial dervaitve of f with respect to y evaluate at (0,0) is equal to [f(0,100) - f(0,0)] / 100 =-1/2
Gradient of f at (0,0) = (1/4, -1/2)
So we suggest going in the direction (-1/4, 1/2) [answer] which is in the direction opposite to the gradient.
======================
Now there are three subtle points that I don't understand:
1. WHY can you use the estimate that partial dervaitve of f with respect to x evaluate at (0,0) is equal to [f(100,0) - f(0,0)] / 100? This is like taking the secant line to be equal to the tangent line, but intution tells me that this estimate can be way way off...
2. Is there any possible way to find the formula for the function of the dome in question (half-sphere)?
3. (-1/4, 1/2) is in the direction opposite to the gradient, why does this give the answer? Pointing in the direction of maximum rate of decrease of f doesn't necessary mean that it's pointing to the absolute minimum of f (i.e. top of dome), right? If I am right, then (-1/4, 1/2) can't be correct...
Thanks for explaining! I really appreciate your help!
Let f(x,y)=depth.
What I've seen in the model solutions is that they used the estimate that
the partial dervaitve of f with respect to x evaluate at (0,0) is equal to [f(100,0) - f(0,0)] / 100 = 1/4,
& the partial dervaitve of f with respect to y evaluate at (0,0) is equal to [f(0,100) - f(0,0)] / 100 =-1/2
Gradient of f at (0,0) = (1/4, -1/2)
So we suggest going in the direction (-1/4, 1/2) [answer] which is in the direction opposite to the gradient.
======================
Now there are three subtle points that I don't understand:
1. WHY can you use the estimate that partial dervaitve of f with respect to x evaluate at (0,0) is equal to [f(100,0) - f(0,0)] / 100? This is like taking the secant line to be equal to the tangent line, but intution tells me that this estimate can be way way off...
2. Is there any possible way to find the formula for the function of the dome in question (half-sphere)?
3. (-1/4, 1/2) is in the direction opposite to the gradient, why does this give the answer? Pointing in the direction of maximum rate of decrease of f doesn't necessary mean that it's pointing to the absolute minimum of f (i.e. top of dome), right? If I am right, then (-1/4, 1/2) can't be correct...
Thanks for explaining! I really appreciate your help!