开方后再平方，输出的值和原值相等，但和原值比较时值却不相等!好疑惑，试了试C语言结果也一样！
a = 2.0 b = 4.0 x = math.sqrt(a) y = math.sqrt(b) print x,y print a,x*x print b,y*y print x*x==a print y*y==b 结果： 1.41421356237 2.0 2.0 2.0 4.0 4.0 False True
int main(void)
{
double a = 2.0,b = 4.0;
double c,d;
c = sqrt(a);
d = sqrt(b);
printf("%f,%f\n",a,b);
printf("%f,%f\n",c*c,d*d);
if(a == c*c) printf("TURE");
else printf("FALSE");
printf(",");
if(b == d*d) printf("TURE");
else printf("FALSE");
return 0;
}
结果：
2.000000,4.000000
2.000000,4.000000
FALSE,TURE
