Triangle
A triangle is a plane figure with three straight sides and three angles. The angle formed inside the triangle is equal to 180 degrees. It means that the sum of the interior angles of a triangle is equal to 180°.
A triangle is a plane figure with three straight sides and three angles. The angle formed inside the triangle is equal to 180 degrees. It means that the sum of the interior angles of a triangle is equal to 180°.
Types of Triangle
Based on the angles and side length, the triangles are classified into six types.
Based on the length of the sides, the triangle is classified into:

Based on the angles, the triangles are classified as:
Acute Angle Triangle – All the angles of a triangle are less than 90 degrees  
Obtuse Angle Triangle – One of the angles of a triangle is greater than 90 degrees  
Right Angle Triangle – One of the angles of a triangle is equal to 90 degrees 
Area and Perimeter


a is the length of the base of the triangle, and h is the height or altitude of the triangle.

Sum of Angles of a Triangle
In a Euclidean space, the sum of angles of a triangle equals a straight angle (180 degrees) 
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