# If else Exercises

**C program to check whether triangle is equilateral, scalene or isosceles**

Write a C program to input sides of a triangle and check whether a triangle is equilateral, scalene or isosceles triangle using if else. How to check whether a triangle is equilateral, scalene or isosceles triangle in C programming. Logic to classify triangles as equilateral, scalene or isosceles triangle if sides are given in C program.

Example

Input

Input first side: 30

Input second side: 30

Input third side: 30

Output

Triangle is equilateral triangle

**Required knowledge**

Basic C programming, Relational operators, Logical operator, If else

**Properties of triangle**

1.A triangle is said Equilateral Triangle, if all its sides are equal. If a, b, c are three sides of triangle. Then, the triangle is equilateral only if a == b == c.

2.A triangle is said Isosceles Triangle, if its two sides are equal. If a, b, c are three sides of triangle. Then, the triangle is isosceles if either a == b or a == c or b == c.

3.A triangle is said Scalene Triangle, if none of its sides are equal.

#### Logic to check equilateral, scalene or isosceles triangle

Step by step descriptive logic to classify triangle as equilateral, scalene or isosceles triangle.

1.Input sides of a triangle from user. Store it in some variables say side1, side2 and side3.

2.Check if(side1 == side2 && side2 == side3), then the triangle is equilateral.

3.If it is not an equilateral triangle then it may be isosceles. Check if(side1 == side2 || side1 == side3 || side2 == side3), then triangle is isosceles.

4.If it is neither equilateral nor isosceles then it scalene triangle.

**Program to check equilateral, scalene or isosceles triangle**

/** * C program to check whether a triangle is Equilateral, Isosceles or Scalene */ #include <stdio.h> int main() { int side1, side2, side3; /* Input sides of a triangle */ printf("Enter three sides of triangle: "); scanf("%d%d%d", &side1, &side2, &side3); if(side1==side2 && side2==side3) { /* If all sides are equal */ printf("Equilateral triangle."); } else if(side1==side2 || side1==side3 || side2==side3) { /* If any two sides are equal */ printf("Isosceles triangle."); } else { /* If none sides are equal */ printf("Scalene triangle."); } return 0; }

**Output**

Enter three sides of triangle: 30

30

30

Equilateral triangle.