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A triangle is a three- sided polygon having three angles. Thus, there are six basic types of triangles, three are classified according to their sides and the other three are classified according to their angles. Let us discuss the different types of triangles and their properties in detail.

Classification by sides (length of their sides)

In an equilateral triangle, all the sides are congruent. That is, all three sides of the triangle are equal. Since all the sides are equal, all the interior angles will also be equal. To find the measure of each angle, an important property of a triangle is to be recalled. ‘The sum of the angles of a triangle is 180 degrees’. Thus dividing 180 to three equal parts, it’s 60. Each angle of an equilateral triangle is 60 degrees. Therefore, an equilateral triangle is also known as an equiangular triangle. 


In an isosceles triangle, only two sides are equal. If two sides are equal, then their angles will also be equal. Thus, the angles opposite to the equal sides are equal. 


By now, you should have guessed it right. A scalene triangle is a triangle in which all three sides are unequal. Thus all three angles are different. In other words, no two angles are equal in a scalene triangle. 


Classification by angles (interior angles)


In an acute triangle, all three interior angles are acute. An acute angle is an angle less than 90 degrees. It also means that all three angles of an acute triangle are less than 90 degrees.


In an obtuse triangle, one angle of the triangle is always greater than 90 degrees, which is called obtuse. Thus a triangle in which one of the angles measures more than 90 is an obtuse triangle.


In a right triangle, one angle is always equal to 90 degrees. The representation of this triangle is shown below. The side opposite to the right angle will be the longest side and is called the hypotenuse. 



Identify Triangles based on sides (no measure)

Identify Triangles based on sides (congruent)

Identify Triangles based on angles

Identify Triangles based on angles (no measure)

Identify Triangles based on sides and angles

Match the following based on sides and angles

Choose the right option based on sides and angles

Triangles based on their sides and angles. 


You also have triangles called acute- equilateral triangle, acute- isosceles triangle,  acute- scalene triangles, right- scalene triangle, right- isosceles triangle, obtuse- scalene triangle, and obtuse- isosceles triangle.





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