Least squares approximation of a function?

Click For Summary
SUMMARY

The discussion focuses on finding the least squares approximation of the function cos^3(x) using a combination of sin(x) and cos(x) over the interval (0, 2π). The correct approximation is stated as sin(x) + (3/4)cos(x), although there is uncertainty regarding its derivation. Participants emphasize the necessity of understanding the principles of least squares regression, particularly in the context of functions rather than vectors. The conversation highlights the importance of grasping the foundational definitions and methodologies associated with least squares approximations.

PREREQUISITES
  • Understanding of least squares regression principles
  • Familiarity with trigonometric functions, specifically sin(x) and cos(x)
  • Basic knowledge of vector representation in mathematical contexts
  • Ability to interpret mathematical approximations and their implications
NEXT STEPS
  • Study the derivation of least squares approximations for functions
  • Explore resources on the mathematical properties of trigonometric functions
  • Learn about vector spaces and their applications in least squares problems
  • Review the normal equations in the context of function approximation
USEFUL FOR

Students in mathematics, particularly those studying calculus and linear algebra, as well as educators and anyone involved in mathematical modeling and function approximation techniques.

DerpyPenguin
Messages
3
Reaction score
0

Homework Statement


Find the least squares approximation of cos^3(x) by a combination of sin(x) and cos(x) over the interval (0, 2pi)

Homework Equations

The Attempt at a Solution


I know how to find a least squares approximation with vectors, but I don't even know how to start with a function? The normal equation wouldn't work here because there are no vectors correct? The answer in the back of the book gives sin (x)+(3/4)cos(x), but I don't even know what that answer means. Please help.
 
Physics news on Phys.org
You won't be able to do it by folowing a formula... you need to understand what least squares regression is and apply the principle. The formula for vectors should have been derived for you. Note: cos and sin are vectors.

So if you had an arbitrary vector, ##\vec a## and you needed it in terms of two other vectors ##\vec u## and ##\vec v##... how would you go about it?
 
Last edited:
DerpyPenguin said:

Homework Statement


Find the least squares approximation of cos^3(x) by a combination of sin(x) and cos(x) over the interval (0, 2pi)

Homework Equations

The Attempt at a Solution


I know how to find a least squares approximation with vectors, but I don't even know how to start with a function? The normal equation wouldn't work here because there are no vectors correct? The answer in the back of the book gives sin (x)+(3/4)cos(x), but I don't even know what that answer means. Please help.

Perhaps you don't know what the answer means because you don't know the definition of least squares approximations for functions. Surely it is in your text. Or looking here:

http://homepage.math.uiowa.edu/~atkinson/ftp/ENA_Materials/Overheads/sec_4-7.pdf

might help you get started. Also, I think your text answer isn't correct.
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 40 ·
2
Replies
40
Views
5K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 14 ·
Replies
14
Views
2K
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 2 ·
Replies
2
Views
1K
Replies
5
Views
2K