Geometry is all about angles, sides and dimensions. Learning Geometry is an essential part of education systems around the world. Having at least the basic knowledge of geometry is essential for everyone. Triangle, rectangle, circle this type of two-dimensional shapes and sphere, cube, pyramids and cylinders etc. are the three-dimensional shapes are there in Geometry. For now, we will see how many types of triangles are there in Geometry along with their definitions. The types of triangles are based on their sides and angles. Let’s every type of triangle.

### Types of Triangles Based on Sides

Triangles are made of three sides. These types are determined by the similarity between the length of those sides. There are three types of triangles based on its sides.

### Equilateral Triangle

**Equilateral Triangles** has all** three equal sides**. All these three equal sides create **three equal internal angles of 60°** each.

An** Isosceles triangle** has two equal sides. There are two equal internal angles in this type of triangles. The name Isosceles derives from the Greek *iso* (same) and *Skelos* (legs).

### Scalene Triangle

Scalene triangles have its all three sides with different lengths. The all the three angles are also different.

Triangles are also categorised based on the internal angles of them. Following are types of triangles based on their internal angles.

### Acute Triangle

Acute triangles have all three acute(less than 90°) angles. If *c* is the length of the longest side, then *a*^{2} + *b*^{2} > *c*^{2}, where *a* and *b* are the lengths of the other sides.

### Obtuse Triangle

Obtuse triangles have one interior angle measuring more than 90°. If c is the length of the longest side, then a2 + b2 < c2, where a and b are the lengths of the other sides.

### Right Triangle

Right Angle Triangles have one angle of 90° from its three angles. The side opposite to the right angle is called **hypotenuse**, which is the longest side of the triangle. The other two sides are called the legs or catheti of the triangle. Right triangles obey the **Pythagorean theorem** which states that the sum of the squares of the lengths of the two legs is equal to the square of the length of the hypotenuse: a2 + b2 = c2, where a and b are the lengths of the legs and c is the length of the hypotenuse.

The triangles are categorised based on the sides and internal angles.

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