头歌作业C语言数学运算练习题

1

#include <stdio.h>

int main() {
	double a, b, c;
	scanf("%lf%lf%lf", &a, &b, &c);
	if (a + b > c && a + c > b && b + c > a)
		printf("1\n");
	else
		printf("0\n");
	return 0;
}

2

#include <stdio.h>
#include <math.h>

int main() {
	float a, b, c, cosA, sinA;
	printf("");
	scanf("%f%f%f", &a, &b, &c);
	if (a + b > c && a + c > b && b + c > a) {
		cosA = (b * b + c * c - a * a) / (2 * c * b);
		sinA = sqrt(1 - (cosA * cosA));
		float area = b * c * sinA * 0.5;
		printf("面积：%.2f", area);
	} else
		printf("无法构成三角形\n");
	return 0;
}

3

#include <stdio.h>

int main() {
	int a;
	int i = 0;
	printf("");
	scanf("%d", &a);
	if (a % 2 == 0) {
		printf("偶数\n", a);
	}
	if (a % 2 != 0) {
		for ( i = 2; i < a; i++) {
			if (a % i == 0)
				break;
		}
		if (i < a) {
			printf("奇数\n");
		} else {
			printf("素数\n");
		}
	}

	return 0;
}

4

#include <stdio.h>
#include <math.h>

int main () {
	double a, b, X;
	scanf("%lf%lf", &a, &b);
	printf("X=%.2lf", (b + sqrt(b * b + 2 * a)) / (a - b));
	return 0;
}

5

#include <stdio.h>
#include <math.h>

int main() {
	int a, x1, x2, x3;
	printf("");
	scanf("%d", &a);
	x1 = a / 100;
	x2 = (a % 100) / 10;
	x3 = a % 100 % 10;
	printf("%d %d %d", x3, x2, x1);
	return 0;
}

6

#include <stdio.h>

int main() {
	int a;
	int N = 0;
	int i, j;
	for (i = 10000; i <= 99999; i++) {
		a = i;
		j = 0;
		while (a) {
			j = a % 10;
			if (j == 4)
				break;
			a /= 10;
		}
		if (j != 4)
			N++;
	}
	printf("10000~99999中不包含4的个数为:%d", N);
	return 0;
}

7

#include <stdio.h>
#include <math.h>
int main()

{
	double a, b, c, d, x1, x2;

	printf ("");

	scanf ("%lf %lf %lf", &a, &b, &c);

	d = b * b - 4 * a * c;

	if (a == 0 )

	{
		printf ("系数a不能为零\n");

		return 1;

	}
	if (d < 0 )

	{
		printf ("方程无实根\n");

		return 1;

	}

	x1 = (-b + sqrt(d)) / (2 * a);

	x2 = (-b - sqrt(d)) / (2 * a);


	printf ("x1=%.2f x2=%.2f\n", x1, x2);

}