We classify triangles depending on their sides (equilat. Triangle ABC is an isosceles obtuse angled triangle, obtuse angled at B and ABBC and O is circumcentre of ABC, OL & OH are perpendicular bisector of AB and. The sum of the lengths of the sides of the isosceles triangle is called its perimeter. Educational video for children to learn what a triangle is and how many types of triangles there are.
![isosceles obtuse isosceles obtuse](https://vt-vtwa-assets.varsitytutors.com/vt-vtwa/uploads/problem_question_image/image/23624/2.png)
Conversely, if the base angles of a triangle are equal, then the triangle is isosceles.” Concept: Classification of Triangles (On the Basis of Sides, and of Angles) - Isosceles Triangles.
![isosceles obtuse isosceles obtuse](https://us-static.z-dn.net/files/d18/68412bb098e8e8a0b1a7308660f977ab.png)
The three sides of the triangle above are AB, BC and AC. An exterior angle of a triangle is formed by any side of a triangle and the extension of its adjacent side. These angles are also called the interior angles of a triangle. The angle formed at A can also be written as ∠BAC. The three angles are the angles made at these vertices, i.e. In the above triangles, the three vertices are A, B and C.