Solving a quadratic Lagrange interpolant , How ?

In summary, the conversation is about a problem involving finding the values of a0, a1, and a2 using MATLAB. The problem involves three equations and three unknowns, which are then written in matrix form. However, the resulting answer is incorrect, leading to confusion about the correct solution. The conversation ends with a request for help before the submission deadline.
  • #1
uaeXuae
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http://img151.imageshack.us/img151/5562/updatequicklyte1.jpg



how would i solve it using MATLAB ? I tried many times but i didnt get the same answer may anyone help me please ?
 
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  • #2
Anyone please ? I have to submit this in 2 days please help...


My attempt is as follows

v(15)=a0+a1(t)+a2(t)=24
a0+a1(15)+a2(15)^2=24


v(18)=a0+a1(t)+a2(t)=37
a0+a1(18)+a2(18)^2=37

v(22)=a0+a1(t)+a2(t)=25
a0+a1(22)+a2(22)^2=25


I then wrote it in the Matrix Form

a=[1 15 225;1 18 324;1 22 484]
b=[24;27;35]
x=a/b

Results:

a0=-323.8571
a1=38.9048
a2=-1.0476


Using the following Equation:

v(16)=-323.8571+(38.9048*16)+(-1.0476*(16^2))=
30.4341 s which is wrong ofcourse The ans is 20.846 so wheres my mistake
 
  • #3
The value 26m/s is obtained twice

First interval: 15 -18
Second Interval: 18-22

So i should be getting two answers is that so ?
 
  • #4
Anyone please help me submission is tommrow
 

1. How do you solve a quadratic Lagrange interpolant?

To solve a quadratic Lagrange interpolant, you need to follow these steps:

  • First, gather the data points that you want to interpolate.
  • Next, use the Lagrange interpolation formula to create a quadratic polynomial that passes through all the data points.
  • Solve the system of equations created by setting the polynomial equal to the data points.
  • Simplify the polynomial to get the final quadratic Lagrange interpolant.

2. What is the Lagrange interpolation formula?

The Lagrange interpolation formula is a mathematical method for finding a polynomial that passes through a set of data points. For a set of n data points, the formula is:
P(x) = Σi=0n (yi * li(x))
Where P(x) is the polynomial, yi is the value of the data point at xi, and li(x) is the Lagrange basis polynomial for the ith data point.

3. What is a quadratic Lagrange interpolant used for?

A quadratic Lagrange interpolant is used to estimate values between known data points. It is commonly used in scientific and engineering applications to fill in missing data or to make predictions based on existing data.

4. What are the limitations of a quadratic Lagrange interpolant?

A quadratic Lagrange interpolant is limited by the accuracy of the data points used. If the data points are not evenly spaced or do not accurately represent the overall trend, the interpolant may not accurately reflect the true values. Additionally, the interpolant is only accurate within the range of the data points and may not accurately predict values outside of that range.

5. How can you improve the accuracy of a quadratic Lagrange interpolant?

To improve the accuracy of a quadratic Lagrange interpolant, you can increase the number of data points used. This will result in a more complex polynomial and a more accurate estimation. Additionally, using evenly spaced data points and ensuring they accurately represent the overall trend can also improve the accuracy of the interpolant.

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