c++ code help !

Discussion in 'Homework Help' started by salam, Nov 22, 2012.

1. salam Thread Starter New Member

Oct 29, 2012
3
0
Hello guys !
I have this homework .. my instructor wants us to solve the following question using c++
Determine the value of F(x) using lagrange polynomials method for the following data
Xi=-1.5 , -0.75 , 0 , 0.75 ,1.5
Yi=-14.1014 , -0.931596 , 0 , 0.931596, 14.1014

Here is my code .. but it only finds the summation , I guess I have to define some character value to use it in printing the formula F(x),, but I couldn't apply this idea .. any help ??

Code ( (Unknown Language)):
1. #include <iostream.h>
2. #include <stdlib.h>
3. #include <math.h>
4.
5. void main ()
6. {
7.     double  X[5],Y[5];
8.     double n=5,sum=0,x;
9.
10.     cout <<"Insert the value x: \n";
11.     cin >>x;
12.
13.
14.     cout <<"Enter vector X : \n" ;
15.     for (int a=0;a<n;a++)
16.     {
17.         cin>>X[a];
18.         cout <<X[a]<<endl;
19.     }
20.     cout<<endl;
21.
22.
23.
24.     cout <<"Enter vector Y : \n" ;
25.     for (int b=0;b<n;b++)
26.     {
27.         cin>>Y[b];
28.         cout <<Y[b]<<endl;
29.     }
30.     cout<<endl;
31.
32.
33.
34.     for (int i=0;i<n;i++)
35.     {
36.         double p=1;
37.         for (int j=0;j<n;j++)
38.         {
39.             if (j!=i)
40.             {
41.                 p=p*((x-X[j])/(X[i]-X[j]));
42.             }
43.         }
44.         sum=sum+p*Y[i];
45.
46.     }
47. cout <<"SUM = \n " << sum <<endl;
48.
49. }
50.
51. [/i][/i][/b][/b]

where x=1.4 , and sum will equal to 11.1984