>>30
#include <stdio.h>
#include <math.h>
/* 階乗 */
double factorial(unsigned int a)
{
    int ans = 1;
    while(a) {
        ans *= a;
        a--;
    }
    return (double)ans;
}
int main()
{
    int n;
    double x,ans = 0.0;
    printf("n?:");
    scanf("%d", &n);
    printf("theta(rad)?:");
    scanf("%lf", &x);
    while(n>0) {
        ans += ( pow(-1,(n-1)) / factorial(2*n-1) * pow(x,(2*n-1)) );
        n--;
    }
    printf("左辺:%lf", sin(x));
    printf("右辺:%lf",ans);

    return 0;
}
ある範囲超えると大幅に狂う…　制限区間があったかも