程序遇到无效指令并关闭 ？

#include<stdio.h>
#include<math.h>
void main()
{
    float *x, *y;
    void change(float *x, float *y);
    printf("input x,y:\n");scanf("%f%f", x, y);
    change(x, y);
    printf("%f,%f", *x, *y);
}
void change(float *x,float *y)
{
    float s=*x, p=*y;
    s = pow((s) * (s) + (p) * (p), 1.0 / 2);
    //p = pow(tan((p) / (s)), -1);
    p=tan(p/s);
    p=p/1;
    *x = s;*y = p;
}
----------------解决方案--------------------------------------------------------
定义时这样 float a,b,*x=&a,*y=&b;
或者
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main()
{
    float x,y;
    void change(float *, float *);
    printf("input x,y:\n");
    scanf("%f%f",&x,&y);
    change(&x,&y);
    printf("%f\t%f\n",x,y);
    system("pause");
    return 0;
}
void change(float *x,float *y)
{
    float s=*x,p=*y;
    s=pow((s)*(s)+(p)*(p),1.0/2);
    p=tan(p/s);
    p=p/1;
    *x=s;
    *y=p;
}
----------------解决方案--------------------------------------------------------
#include<stdio.h>
#include<math.h>
void main()
{
    float *x,*y;
    float a,b;
    void change(float *x,float *y);
    x=&a;
    y=&b;
   
    printf("input x,y:\n");
    scanf("%f%f",&a,&b);
    change(&a,&b);
    printf("%f,%f",*x,*y);
}
void change(float *x,float *y)
{
    float s=*x, p=*y;
    s = pow((s) * (s) + (p) * (p), 1.0 / 2);
    /*/p = pow(tan((p) / (s)), -1);*/
    p=tan(p/s);
    p=p/1;
    *x = s;*y = p;
}
----------------解决方案--------------------------------------------------------