A triangle is created of 3 line segments. The heat segments intersect in your endpoints. To name a triangle we frequently use the vertices (the surname of the endpoints). The triangle below is called ABC.

You are watching: A triangle with at least two congruent sides


A triangle has three angles. The sum of the steps of the angles is always 180° in a triangle.

We have actually different species of triangles. A triangle is classified by its angles and also by the variety of congruent sides.

A triangle that has actually three acute angels is referred to as an acute triangle.


A triangle that has actually one appropriate angle is called a appropriate triangle.


A triangle that has one obtuse edge is dubbed an obtuse triangle.


When a triangle has three congruent sides, we speak to the triangle an it is intended triangle. We note the congruent political parties by a cut mark. The angle in an it is provided triangle are always 60°.


When a triangle has two congruent sides it is called an isosceles triangle. The angle opposite to the two sides of the same size are congruent.


A triangle without any kind of congruent sides or angle is called a scalene triangle.

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When 2 triangles space congruent it means that they have the exact same size and also shape. This means that they have the same angles. The red cut marks show us i m sorry sides and also angles that are congruent Congruency is displayed by this symbol



$$\beginmatrix A\cong X & & AB\cong XY\\ B\cong Y & & BC\cong YZ\\ C\cong Z & & AC\cong XZ \endmatrix$$

Triangles that have congruent angles yet not the very same size are dubbed similar. Comparable triangles have sides that room proportional. Similarity is displayed by this symbol



$$\bigtriangleup ABC\sim \bigtriangleup XYZ$$

$$A=X,\: \: B=Y,\: \: C=Z$$



Find x in the comparable triangles.


We recognize that due to the fact that the triangle are comparable the sides space proportional which means that


$$x=\frac14\cdot 321=\frac4221=2$$


Video lesson

Find out whether the triangles room right, isosceles, acute, scalene, obtuse or equilateral