[Error] 'm' was not declared in this scope

#include <iostream>
#include <conio.h>
#include <cmath>
#include <stdio.h>
using namespace std;
void fun(float m, float h)
{
    float p,y;
    p=m-h;
    if (p<0)
    cout<<"\notricatelnoe chislo v korne!";
    else if (h==0)
    cout<<"\nNa 0 delit nelsa!!!";
    else
{
        y= (sqrt(m-h)/h-tan(m)/pow(h,2));
    printf("\ny=%8.4f",y);}
    return;
}
 int main()
{
    float x,b;
    cout<<"\nx=";
    cin>>x;
    cout<<"\nb=";
    cin>>b;
    cout<<"\nD(f)=(- beskonechnost ,0)i(0,+ beskonechnost)\n";
    fun(m,h);
    getch(); 
    return 0;
}

fun(x,b);

fun(b,x);

#include <iostream>
#include <conio.h>
#include <cmath>
using namespace std;
 
float f(float x, float b)
{
    return (sqrt(x-b)/b-tan(x)/pow(b,2));
}
 
int main()
{
    float x,b;
    cout<<"\nx=";
    cin>>x;
    cout<<"\nb=";
    cin>>b;
    cout<<"\nD(f)=(- beskonechnost ,0)i(0,+ beskonechnost)";
    float p;
    p=x-b;
    if (p<0)
    cout<<"\notricatelnoe chislo v korne!";
    else if (b==0)
    cout<<"\nNa 0 delit nelsa!!!";
    else
    cout<<"\ny="<<f(x,b);
    getch(); 
    return 0;
}

#include <iostream>
#include <conio.h>
#include <math.h>
#include <stdio.h>
 
using namespace std;
void fun(float m, float h)
{
    float p,y;
    p=m-h;
    if (p<0)
    cout<<"\notricatelnoe chislo v korne!";
    else if (h==0)
    cout<<"\nNa 0 delit nelsa!!!";
    else
{
        y=sqrt(m-h)/h-tan(m)/pow(h,2);
    printf("\ny=%8.4f",y);}
    return;
}
 int main()
{
    float x,b;
    cout<<"\nx=";
    cin>>x;
    cout<<"\nb=";
    cin>>b;
    cout<<"\nD(f)=(- beskonechnost ,0)i(0,+ beskonechnost)\n";
    fun(x,b);
    getch();
    return 0;
}