### Math - Class 5 – Classify triangles (Geometry practice)/ Triangle angle-sum property /Classifying Triangles/ Triangles and their types /Properties of Triangles / Facts about a Triangle – Key Points/Notes/Worksheets/Explanation/Lesson/Practice Questions

**Tags:**Triangle Classification, Classifying Triangles by Sides or Angles for class 5, Free downloadable Worksheet PDF on Triangle for 5th class, Practice questions and examples with solution on Triangles for fifth standard, Lesson on Classification of Triangles for Grade V, Classification of triangle according to angles and sides, What is scalene triangle? What is obtuse triangle? What is acute triangle? What is equilateral triangle? Right angled triangle, Acute angled triangle, Obtuse angled triangle, Sum of the angles in a triangle, Triangles and its properties, Some fact about triangle, Properties of a triangle, Difference between equilateral and equiangular triangle. Classify the triangles into acute, obtuse and right angled triangle with following angles: 30°, 90°, 60°, Classify triangles according to sides as equilateral, isosceles or scalene triangle. 5cm, 3cm, 6cm, If two angles of a triangle measures 50° and 60°. Find the measure of the third angle of the triangle. The three angles of a triangle are in the ratio of 2:3:5. Find the measure of each angle of the triangle. Find the third angle and mention the kind of triangle. ∠A = 80°, ∠B = 40°, ∠C =? Can we have a triangle with the following angles and sides? Justify your answer with reason. 50°, 90°, 60°### Classification of Triangles

Since there are two main elements in any triangle, that are its sides and angles.

So, triangles are classified, or grouped, in two different ways.

a) On the basis of sides

b) On the basis of angles

__Classification of triangles on the basis of sides__**Scalene Triangle**A triangle in which all three sides are of different length (non-congruent) is called a

__scalene triangle__.**Isosceles Triangle**A triangle in which two of its sides are equal in length (i.e. two sides are congruent) is called an

__isosceles triangle__. (The slash marks indicate equal measure.)**Equilateral Triangle**A triangle which has all its three sides are of equal length (i.e. all sides are congruent) is called an

__equilateral triangle__. (The slash marks indicate equal measure.)__Classification of triangles on the basis of angles__**Acute Angled Triangle**A triangle whose all three angles are acute, that is

__less than 90°__is called an__acute angled triangle or acute triangle__.**Obtuse Angled Triangle**A triangle whose one angle is obtuse, that is

__more than 90° but less than 180°__is called an__obtuse angled or obtuse triangle__.**Right Angled Triangle**A triangle whose one angle is a

__right angle (that is 90°)__is called a__right angled triangle or right triangle.__**Equiangular Triangle**A triangle which has all its three angles are of

__equal measurement i.e. 60°__is called an__equiangular triangle__.The sides of an

__equiangular triangle__are all the same length (congruent), and so an equiangular triangle is really the same thing as an__equilateral triangle__.__Properties of Triangles__The sum of three angles of a triangle equals to 180°.__Property 1:__So, if two angles of a triangle are given, we can easily find out its third angle.

__Property 2__**:**The sum of the lengths of any two sides of a triangle is greater than the length of the third side.This mean if we add any two side of the triangle, the sum is more than its third side.

#### Some More Facts About A Triangle

- If all the three sides of a triangle are equal, then all its three angles are also equal. This mean an equilateral triangle is also an equiangular triangle.
- In an isosceles triangle,
the angles opposite to the equal sides are equal.
- An acute angled triangle
may be scalene, isosceles or equilateral.
- In an obtuse angled
triangle, the side opposite to the obtuse angle is the longest