## What is a triangle?

A Polygon which has three sides or three edges and three vertices is known as the triangle. The sum of all 3 angles of a triangle always equals to 180°. Three or two sides of the triangle can be equal and unequal in the triangle and it depends on the type of triangle.

### Type of triangle on the basis of sides

There are seven types of the triangle and their names are mentioned below:

1. Equilateral triangle: one whose three equal sides and equal angles. All angle is 60°.

2. Isosceles triangle: one whose two sides are equal and equal angles.

3. Scalene triangle: one whose all sides are not equal. Triangle Description Equilateral triangle Three Side equal Isosceles triangle Two Side equal Scalene triangle No Side equal

### Type of triangle on the basis of sides

1. Right triangle: one whose one angle is right angle(90°).

2. Acute triangle: one whose all angle is acute angle.

3. Obtuse triangle: one whose one angle is obtuse angle.

4. Oblique triangle: An oblique triangle is any triangle that is NOT a right triangle. Acute triangles and obtuse triangles are oblique triangles.

 Triangle Description Acute triangle all angle is acute Obtuse triangle one angle is obtuse Right triangle one angle is right angle (90°)

### Area of a triangle

In case of calculating the area of a triangle, you have to multiply the base of the triangle by the height of the triangle and then divide by 2. So, the digit you will get, it will be the area of that triangle.

##### Formula to find the area of a triangle: –

Area = base x height2

Where
b is base of the triangle & h is the height of triangle. Example:
Find the area of the triangle which has base 10 cm and height 9 cm?

Solution:
Where,
b = 10 cm
h = 9 cm
Formula to find the area of triangle is,
A = (b x h)2
Then,
A = (10 x 9)2
A = 902
A = 45 cm2

### Find the area of triangle without the height

When, in any question the height has not given, then we use the Hero’s formula.
Hero’s formula for finding the area of a triangle is:

√s (s-a) (s-b) (s-c)

In this formula,
S is stand for the semi-perimeter or half perimeter and a, b, c are the sides of triangle Example: Find the area of triangle a = 9, b = 7, c= 4 and s = 10 ### What is the perimeter?

The perimeter is the length of the boundary of any polygon. In other words, the perimeter can be also defined as the path surrounded by any polygon. The word perimeter derives from the Greek word “peri” which means around and “metron” means measure. The total length of the side of any polygon is referred to as perimeter.

### Formula to find the perimeter of a triangle:

The perimeter of triangle ABC

P = AB+BC+CA

Where,
AB, BC, and CA are referring the three sides of a triangle. Example
Find the perimeter of the triangle which has AB = 8 cm, BC = 13 cm and CA= 11 cm. The formula for finding the perimeter of triangle ABC= AB + BC + CA

SO,
AB = 8 cm
BC = 13 cm
CA = 11 cm

After applying the value in formula,

Perimeter of triangle ABC = 8 + 11 + 13
= 32 cm

I hope this, the article will help you to prepare for an RRB NTPC exam. If you have any question related to the article, you can post it into the comment section. You will get a reply shortly.