Write a program to find the area under the curve y = f(x) between x = a and x = b, integrate y = f(x) between the limits of a and b. The area under a curve between two points can be found by doing a definite integral between the two points.
Solution:
#include
float start_point, /* GLOBAL VARIABLES */
end_point,
total_area;
int numtraps;
main( )
{
void input(void);
float find_area(float a,float b,int n); /* prototype */
print(“AREA UNDER A CURVE”);
input( );
total_area = find_area(start_point, end_point, numtraps);
printf(“TOTAL AREA = %f”, total_area);
}
void input(void)
{
printf(“\n Enter lower limit:”);
scanf(“%f”, &start_point);
printf(“Enter upper limit:”);
scanf(“%f”, &end_point);
printf(“Enter number of trapezoids:”);
scanf(“%d”, &numtraps);
}
float find_area(float a, float b, int n)
{
floatbase, lower, h1, h2; /* LOCAL VARIABLES */
float function_x(float x); /* prototype */
float trap_area(float h1,float h2,floatbase);/*prototype*/
base = (b-1)/n;
lower = a;
for(lower =a; lower <= b-base; lower = lower + base)
{
h1 = function_x(lower);
h1 = function_x(lower + base);
total_area += trap_area(h1, h2, base);
}
return(total_area);
float trap_area(float height_1,float height_2,floatbase)
{
float area; /* LOCAL VARIABLE */
area = 0.5 * (height_1 + height_2) * base;
return(area);
}
float function_x(float x)
{
/* F(X) = X * X + 1 */
return(x*x + 1);
}
Output
AREA UNDER A CURVE
Enter lower limit: 0
Enter upper limit: 3
Enter number of trapezoids: 30
TOTAL AREA = 12.005000
AREA UNDER A CURVE
Enter lower limit: 0
Enter upper limit: 3
Enter number of trapezoids: 100
TOTAL AREA = 12.000438