Nowadays, we study various types of shapes which is useful in day to day life. These shapes are used in building elevation, flooring, fashion designing, and various arts.

In this article, we are discussing triangle and it's various topics.

Here is the content of our mini-guide on the triangle which will help you as a beginner.

So first we start with the definition of a triangle and discuss parts of a triangle.

# 1. What is a triangle?

Triangle is a simple closed shape which is made only from three line segments.

Triangle is a polygon of three sides.

Triangle is a simple closed shape with three vertices.

## 2. Parts of a triangle

**Side**

**Angle**

**Interior Angle**

### Median

Triangle has three sides, three vertices, three interior angles.

We explained triangles & components of triangles now we need to explain the types of triangles.

## 3. Types of triangles

*Types of triangles based on sides-*

### Equilateral triangle

### Isosceles triangle

### Scalene triangle

*Types of triangles based on angles-*

### Right-angled triangle

### Acute angled triangle

### Obtuse angled triangle

Generally, we learn above all kinds of the triangle.

But when a triangle contains two properties(based on their sides & angles) then we must study the below triangle.

*Types of triangles based on both angles and sides-*

### Acute-angled equilateral triangle

### Right-angled isosceles triangle

### Obtuse-angled scalene triangle

## 4. Properties of triangle

There are several properties of the triangle which helps to solve the questions.

Let's discuss it one by one-

### Pythagoras theorem (Pythagoras property of right triangle)

It states - In a right-angled triangle square of the longest side is equal to the sum of the square of the other two sides.

**H² = P² + B²**

### Angle sum property of triangle

**∠A + ∠B + ∠C = 180°**

### Exterior angle property of triangle

**x° + y° = Exterior angle**

**Sum of two sides of the triangle**

It states the sum of any two sides of a triangle is always greater than its third side.

## 5. Area of triangle

Area of triangle is the region surrounded by sides of a triangle.

We have several formulas to find the area of a triangle. Let's discuss-

### Area of a right-angled triangle(Right triangle)

**ar∆ = 1/2×Base×Height**

### Area of an equilateral triangle

**ar∆ = √3/4×side²**

### Heron's Formula

**ar∆ = √{s(s-a)(s-b)(s-c)}**

## 6. Perimeter of triangle

The perimeter of a triangle is the length of its boundary.

*The formula for the perimeter of a triangle = The sum of the length of all sides.*

*(for equilateral triangle)*

## 7. Congruence of a triangle

When all sides and angles of a triangle are equal to the corresponding sides and angles of another triangle then both triangles are congruent to each other.

*There are various rules for the congruence of the triangle-*

### SSS congruence rule (Side-Side-Side)

### ASA congruence rule (Angle-Side-Angle)

### SAS congruence rule (Side-Angle-Side)

When any two sides and an angle of a triangle are equal to the corresponding sides and angle of another triangle so both the triangles are congruent by the Side-Angle-Side (SAS) congruence rule.