## C Programming

### Check the points are co-linear or not

#### Objective:

Input coordinates for 3 points (x1,y1), (x2,y2) and (x3,y3). Write a program to check that all points are fall in one straight line or not.

#### Program / Solution:

```#include<stdio.h>
#include<math.h>

int main() {
int x1,y1,x2,y2,x3,y3;
int s1,s2,s3;

printf("Enter first point (x1,y1): ");
scanf("%d%d",&x1,&y1);

printf("Enter second point (x2,y2): ");
scanf("%d%d",&x2,&y2);

printf("Enter third point (x3,y3): ");
scanf("%d%d",&x3,&y3);

s1 = abs(x2 - x1) / abs(y2 - y1); //slop between point-1 and point-2
s2 = abs(x3 - x2) / abs(y3 - y2); //slop between point-2 and point-3
s3 = abs(x3 - x1) / abs(y3 - y1); //slop between point-3 and point-1

if((s1 == s2) && (s2 == s3)) {
printf("Points are co-linear");
}else {
printf("Points are not co-linear");
}
return 0;
}
```

#### Sample Output:

```Enter first point (x1,y1): 1 1
Enter second point (x2,y2): 2 2
Enter third point (x3,y3): 3 3
Points are co-linear
```