Numerical method Solution of ordinary differential equation using RK4 method in C
Numerical method : Solution of ordinary differential equation using RK4 method in C
Algorithm:
 Start
 Declare and Initialize necessary variable likes K1, K2, K3, K4 etc.
 Declare and define the function that returns the functional value.
 Get the initial value of x, initial value of y, no. of iteration and interval from user.
 for i = 0 to i < n go to step 6.
 Do the following calculation: and go to step 7
 The new values of x and y are: x = x + interval, y = y + K;
 print the value of x and y;
 stop
Flowchart:

Source Code:
#include/******************************************************
Program: solution of ordinary differential equationLanguage : CAuthor: Bibek SubediTribhuvan University, Nepal********************************************************/float func(float x, float y){return (y*yx*x)/(y*y+x*x);}int main(){float K, K1, K2, K3, K4;float x0 , y0, x, y;int j, n; float i, H;printf("Enter initial value of x: ");scanf("%f", &x0);printf("Enter initial value of y: ");scanf("%f", &y0);printf("Enter no iteration: ");scanf("%d", &n);printf("Enter the interval: ");scanf("%f", &H);x = x0;y = y0;for(i = x+H, j = 0; j < n; i += H, j++){K1 = H * func(x , y);K2 = H * func(x+H/2, y+K1/2);K3 = H * func(x+H/2, y+K2/2);K4 = H * func(x+H, y+K3);K = (K1 + 2*K2 + 2*K3 + K4)/6;x = i;y = y + K;printf("At x = %.2f, y = %.4f ", x, y);printf("\n");}return 0;}
Output
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