Finding the Direction of a Function

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Homework Help Overview

The discussion revolves around finding the direction of the function f(x,y)=x^2+sin(4y) that increases most rapidly at the point P0=(1,0) and determining the derivative of f in that direction. The subject area includes multivariable calculus, specifically gradient vectors and directional derivatives.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the necessity of finding the gradient at point P0 and the concept of unit vectors. There is a focus on understanding the relationship between the gradient and the direction of maximum increase. Questions arise about the need for additional points to find a unit vector and the implications of the gradient's magnitude.

Discussion Status

Some participants have provided guidance on the role of the gradient in determining the direction of increase and have prompted further exploration of its magnitude. Multiple interpretations of the gradient's significance are being considered, but there is no explicit consensus on the next steps.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the information they can use or the methods they can apply. There is an ongoing discussion about the correctness of the gradient calculation and its implications for the problem.

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Homework Statement


Find the direction in which the function f(x,y)=x^2+sin(4y) increses most rapidly at the point P0=(1,0). Then find the derivative of f in this direction.


Homework Equations





The Attempt at a Solution


I think I have to find the gradient at point P0 and then find a unit vector is this right?
 
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Ki-nana18 said:

Homework Statement


Find the direction in which the function f(x,y)=x^2+sin(4y) increses most rapidly at the point P0=(1,0). Then find the derivative of f in this direction.


Homework Equations





The Attempt at a Solution


I think I have to find the gradient at point P0 and then find a unit vector is this right?
Yes, for the first part of your question.
 
Okay, I found the gradient <2x+sin(4y), x^2+4cos(4y)> and at point P0 it is
<2,5>. Now if I only have one point how do I find the unit vector wouldn't I need another point or an initial vector?
 
Ki-nana18 said:

Homework Statement


Find the direction in which the function f(x,y)=x^2+sin(4y) increses most rapidly at the point P0=(1,0). Then find the derivative of f in this direction.


The Attempt at a Solution


I think I have to find the gradient at point P0 and then find a unit vector is this right?

What do you need the unit vector for?

Ki-nana18 said:
Okay, I found the gradient <2x+sin(4y), x^2+4cos(4y)> and at point P0 it is
<2,5>. Now if I only have one point how do I find the unit vector wouldn't I need another point or an initial vector?

Your gradient isn't correct. You want ∇f = <fx, fy>.
Then think about this question: What does the gradient have to do with the maximum rate of increase of a function? The answer to that is surely in your text.
 
Sorry. \nablaf=<2x, 4 cos(4y)>. Does the gradient at P0 tell me the direction in which the function increases most rapidly?
 
Ki-nana18 said:
Sorry. \nablaf=<2x, 4 cos(4y)>. Does the gradient at P0 tell me the direction in which the function increases most rapidly?

Yes, and there's more. What does the magnitude of the gradient represent?
 
How fast the function increases?
 
In what direction? A function of several variables may have different rates of increase in different directions.
 

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