A closed figure with three sides is a triangle.
Earlier we have learnt how the triangles are classified based on their sides.
Let us recall the types of triangle based on its sides:
(i) Equilateral triangle
(ii) Isosceles triangle
(iii) Scalene triangle
Now, let us explore how the triangles are classified based on their angles in detail.
The naming of triangles based on angles:
- Type - 1: Acute angled triangle
If all the three angles of the triangle are acute (less than \(90°\)), then it is called an acute angled triangle.
Example:
In here, all the three angles are less than \(90°\). That is, \(∠A=60°, ∠B=50°\) and \(∠C=70°\).
- Type - 2: Right angled triangle
If one of the angles of a triangle is right angle \((90°)\) and the other two are acute angles (less than \(90°\)), then its is called a right angled triangle.
Example:
In here, one among the angle is \(90°\), and the other two are acute. That is, \(∠A=40°, ∠B=50°\) and \(∠C=90°\).
- Type - 3: Obtuse angled triangle
If one of the angles of a triangle is an obtuse angle (greater than \(90°\)), and the other two are acute angle (less than \(90°\)), then it is called an obtuse angled triangle.
Example:
In here, one among the angle greater than \(90°\) and the other two are acute. That is, \(∠A=120°, ∠B=35°\) and \(∠C=25°\).