Finding the Direction of a Function

In summary, the conversation discusses finding the direction in which the function f(x,y)=x^2+sin(4y) increases most rapidly at the point P0=(1,0), and then finding the derivative of f in this direction. The conversation also mentions finding the gradient at point P0 and using it to determine the direction of maximum increase, as well as considering the magnitude of the gradient to determine the rate of increase in that direction.
  • #1
Ki-nana18
91
0

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?
 
Physics news on Phys.org
  • #2
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.
 
  • #3
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?
 
  • #4
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.
 
  • #5
Sorry. [itex]\nabla[/itex]f=<2x, 4 cos(4y)>. Does the gradient at P0 tell me the direction in which the function increases most rapidly?
 
  • #6
Ki-nana18 said:
Sorry. [itex]\nabla[/itex]f=<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?
 
  • #7
How fast the function increases?
 
  • #8
In what direction? A function of several variables may have different rates of increase in different directions.
 

1. What is the purpose of finding the direction of a function?

The direction of a function is important because it tells us whether the function is increasing or decreasing at a specific point. This information can help us analyze the behavior of the function and make predictions about its future values.

2. How do you determine the direction of a function?

To determine the direction of a function, we look at the slope of the function at a specific point. If the slope is positive, the function is increasing, and if the slope is negative, the function is decreasing. Additionally, we can look at the concavity of the function to determine whether it is increasing or decreasing.

3. What is the relationship between the direction of a function and its graph?

The direction of a function is directly related to the shape of its graph. If the function is increasing, its graph will slope upwards from left to right. If the function is decreasing, its graph will slope downwards from left to right. The concavity of the function also affects the shape of its graph, with a concave up function having a graph that curves upwards and a concave down function having a graph that curves downwards.

4. Can a function change direction at a single point?

Yes, a function can change direction at a single point. This is known as a point of inflection and occurs when the concavity of the function changes from positive to negative or vice versa. At this point, the function is neither increasing nor decreasing, but rather changing direction.

5. What are some real-world applications of finding the direction of a function?

Finding the direction of a function has many real-world applications, such as in economics to analyze the trends of a market, in physics to understand the motion of objects, and in engineering to optimize designs and predict the behavior of systems. It can also be used in everyday life, such as determining the best route to take based on traffic patterns or predicting the growth of investments.

Similar threads

  • Calculus and Beyond Homework Help
Replies
8
Views
474
  • Calculus and Beyond Homework Help
Replies
8
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
562
  • Calculus and Beyond Homework Help
Replies
3
Views
287
  • Calculus and Beyond Homework Help
Replies
4
Views
1K
  • Calculus and Beyond Homework Help
Replies
27
Views
740
  • Calculus and Beyond Homework Help
Replies
10
Views
827
  • Calculus and Beyond Homework Help
Replies
6
Views
1K
  • Calculus and Beyond Homework Help
Replies
2
Views
670
  • Calculus and Beyond Homework Help
Replies
7
Views
1K
Back
Top