int i=3;
printf("%d\n",-(i++));
输出的是- 3,而非- 4.
s=a*a*(tan(72.0/180*3.14159265)/4+sin(72.0/180*3.14159265))
而非s=a*a*(1/4*tan(72.0/180*3.14159265)+sin(72.0/180*3.14159265))
亦非
s=a*a*(tan(72/180*3.14159265)/4+sin(72/180*3.14159265))
int i=3;
printf("%d\n",-(i++));
输出的是- 3,而非- 4.
s=a*a*(tan(72.0/180*3.14159265)/4+sin(72.0/180*3.14159265))
而非s=a*a*(1/4*tan(72.0/180*3.14159265)+sin(72.0/180*3.14159265))
亦非
s=a*a*(tan(72/180*3.14159265)/4+sin(72/180*3.14159265))