
If and only if one pair of internal angles of two triangles have the same measure as each other, and another pair also have the same measure as each other, the triangles are similar.Some basic theorems about similar triangles are: The corresponding sides of similar triangles have lengths that are in the same proportion, and this property is also sufficient to establish similarity. Two triangles are said to be similar, if every angle of one triangle has the same measure as the corresponding angle in the other triangle. The sum of the measures of the three exterior angles (one for each vertex) of any triangle is 360 degrees. Since the sides of a triangle correspond to its angles, this means that isosceles triangles also have two angles of equal measure. The measure of an exterior angle of a triangle is equal to the sum of the measures of the two interior angles that are not adjacent to it this is the exterior angle theorem. An isosceles triangle is a triangle that has at least two sides of equal length. An exterior angle of a triangle is an angle that is a linear pair (and hence supplementary) to an interior angle. Ex 7.2,1 In an isosceles triangle ABC, with AB AC the bisectors of B and C interest each other at O. Various formulas for isosceles triangles are explained below. The two angles opposite to the equal sides are equal and are always acute. The transformation underwent for the given vertices is ABC was translated. The two sides that are opposite the two equal base angles are equal in length. This allows determination of the measure of the third angle of any triangle, given the measure of two angles. In geometry, an isosceles triangle is a triangle having two sides of equal length. triangle (B) Isosceles triangle (C) Equilateral triangle (D) Scalene triangle. An isosceles triangle is a type of triangle with the following properties. This fact is equivalent to Euclid's parallel postulate. The sum of the measures of the interior angles of a triangle in Euclidean space is always 180 degrees. The measures of the interior angles of the triangle always add up to 180 degrees (same color to point out they are equal). Elementary facts about triangles were presented by Euclid, in books 1–4 of his Elements, written around 300 BC. In rigorous treatments, a triangle is therefore called a 2- simplex (see also Polytope).

Triangles are assumed to be two- dimensional plane figures, unless the context provides otherwise (see § Non-planar triangles, below). A triangle with vertices A, B, and C is denoted △ A B C īasic facts A triangle, showing exterior angle d. It is one of the basic shapes in geometry.

An isosceles triangle is generally drawn so it is sitting on its base. A triangle is a polygon with three edges and three vertices. An isosceles triangle is a triangle with two congruent sides.
