i am getting infinity in my program !!! ??

this is what i am suppose to do.:

Scan two doubles a and b (a<b).

Integrate numerically y=0.5*cos^2(x)+0.25 from x=a to x=b.

Use two do/while statements to continue the

calculations for different n_trap and different a and b. For

example, use ask=1 to continue calculations for different n_term

within the inner do/while loop, and ask=0 to exit that loop.

Use flag=1 to continue calculations for different a and b

within the outer do/while loop, and flag=0 to exit that loop.

and this is my program so far. btw im only doing the first part havent tried the flag part because im confused

#include <stdio.h>

#include <math.h>

main ()

{

double a, b, y, del_x, Integral, x, sum;

int flag, k, n_trap, ask;

printf("Scan a and b:");

scanf("%1f %1f %1f", &a, &b);

do

{

printf("Enter the number of trapezoids:\n");

scanf("%d", &n_trap);

del_x = (b-a)/(double)n_trap;

printf("n_trap =%d\t del_x =%g\n", n_trap, del_x);

x=a;

y=0.5*cos(x)*cos(x)+0.25;

sum= -0.5 * y;

for(k=0; k<=n_trap; k++)

{

x=a+k*del_x;

y=0.5*cos(x)*cos(x)+0.25;

sum += y;

}

sum -= 0.5*y;

sum += del_x;

printf("Integral = %f\n", sum);

printf("Would you like to continue with another n_trap? y=1/n=0\n");

scanf("%d", &ask);

}

while (ask == 1);

//while (ask !=1 0);

}