自学数学看到这个符号看不懂了

exp
函数名:exp
功 能:指数函数
用 法:double exp(double x);
程序例:
#include
#include
int main(void)
{
double result;
double x = 4.0;
result = exp(x);
printf("'e' raised to the power \
of %lf (e ^ %lf) = %lf\n",
x,x,result);
return 0;
}