求C語言編程矩形面積周長對角線

//面積

double area(double len,double wid){return len*wid;}

//周長

double circle(double len,double wid){return 2*(len+wid);}

//對角線

double duijiaoxian(double len,double wid){return sqrt(len*len+wid*wid);}

void main()

{

printf("請輸入長寬：\n");

double length,width;

scanf("%f%f",&length,&width);

printf("面積為：\n",area(length,width));

printf("周長為：\n",circle(length,width));

printf("對角線長為：\n",duijiaoxian(length,width));

}