# C program to check triangle is equilateral, isosceles or scalene

In this program, take three sides of a triangle as input from the user and check whether the triangle is equilateral, isosceles, or scalene.

## check triangle is equilateral, isosceles or scalene

``````#include <stdio.h>
int main()
{
int s1,s2,s3;
printf("\n enter three side of tringle:");
scanf("%d%d%d",&s1,&s2,&s3);
if((s1==s2)&&(s2==s3))
{
/* if all side are equal */
printf("\n tringle is equilateral");
}
else if((s1==s2)||(s2==s3)||(s1==s3))
{
/* if two side are equal */
printf("\n tringle is isosceles");
}
else
{
/* if all side are diffrent */
printf("\n tringle is scalene");
}
return 0;
}``````

## output

```Run:1
enter three side of tringle:10 10 10
tringle is equilateral
Run:2
enter three side of tringle:10 20 10
tringle is isosceles
Run:3
enter three side of tringle:10 20 30
tringle is scalene```

### Logic to check whether the triangle is equilateral, isosceles, or scalene

• Take three sides of the triangle and store and stored the side in `s1`, `s2`, and `s3`.
• First, you need to check whether all sides are equal or not i.e `(s1 == s2) && (s2 == s3)`. if side `s1` is equal to side `s2` and side `s2` is equal to side `s3` then the triangle is `equilateral`.
• If all sides are not equal then control flow transfer else if part. in else if part, you will check whether any two sides are equal or not i.e `(s1 == s2) || (s2 == s3) || (s1 == s3)`. if any two sides are equal then the triangle is `isosceles`.
• Now if any two sides are not equal then else part will get executed and the triangle is `scalene`.