Why can I see nan?

Question

C++ / C#

#include <stdio.h>
#include <cmath>
#include <math.h>
int main() {

  
  float b =acos(2.5)/asin(2.5);
  printf("%f",b);

}

Answer 1

Sine / cosine can only take values ​​from -1 to 1
, for some reason you have it 2.5