一个关于结构的问题，初学c请指点

#include<stdio.h>
#define N 3
struct triangle
{
    double side1;
    double side2;
    double side3;
};
int a(struct triangel *);
void main()
{
    struct triangle b[N];
    int x,y;
    printf("输入3个三角形的信息\n");
    for(x=0;x<N;x++)
    {
        printf("输入第%d个三角形的三条边长\n",x+1);
        fflush(stdin);
        scanf("%lf%lf%lf",&b[x].side1,&b[x].side2,&b[x].side3);
    }
    for(x=0;x<N;x++)
    {
        y=a(&b[x]);
        if(y==1)
            printf("第%d个三角形为等边三角形\n",x+1);
        else if(y==2)
            printf("第%d个三角形为不等边三角形\n",x+1);
        else if(y==3)
            printf("第%d个三角形为等腰三角形\n",x+1);
    }
}
int a(struct triangle *ptr)
{
    int z;
    if((ptr->side1+ptr->side2+ptr->side3)==ptr->side1*3)
    {
        z=1;
        return z;
    }
    else if((ptr->side1!=ptr->side2)&&(ptr->side1!=ptr->side3)&&(ptr->side2!=ptr->side3))
    {
        z=2;
        return z;
    }
    else
    {
        z=3;
        return z;
    }
}
次程序是用结构判断输入的是哪种类型的三角形，但为什么编译的时候说错误为
error C2664: 'a' : cannot convert parameter 1 from 'struct triangle *' to 'struct triangel *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
但是我用同样的方法实现了。学员信息的处理。请问哪里有问题
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谁能指点一下
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int a(struct triangel *);
拼错了..
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晕。谢谢
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