#include <stdio.h> #include <math.h> int main() { double a,b,c; scanf("%lf %lf %lf",&a,&b,&c); double cosA = (pow(b,2)+pow(c,2)-pow(a,2))/(2*b*c); double sinA = sqrt(1-pow(cosA,2)); printf("circumference=%.2lf area=%.2lf",a+b+c,0.5*b*c*sinA); } 在记不住海伦公式的前提下，用余弦定理计算出si...
