A triangle is created of three line segments. The heat segments intersect in their endpoints. To surname a triangle we regularly use that vertices (the surname of the endpoints). The triangle below is named ABC.

You are watching: Triangle a & e

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

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

A triangle that has three acute angels is dubbed an acute triangle.

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A triangle that has actually one right angle is referred to as a appropriate triangle.

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

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When a triangle has three congruent sides, we contact the triangle an it is intended triangle. We mark the congruent sides by a cut mark. The angle in an equilateral triangle are constantly 60°.

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When a triangle has two congruent political parties it is referred to as an isosceles triangle. The angle opposite come the two sides of the same size are congruent.

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A triangle without any congruent political parties or angles is dubbed a scalene triangle.

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When two triangles are congruent it method that they have actually the exact same size and shape. This method that they have the same angles. The red slash marks show us which sides and also angles that are congruent Congruency is presented by this symbol

$$cong$$

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$$eginmatrix Acong X & & ABcong XY\ Bcong Y & & BCcong YZ\ Ccong Z & & ACcong XZ endmatrix$$

Triangles that have congruent angles however not the exact same size are called similar. Similar triangles have sides that space proportional. Similarity is presented by this symbol

$$sim$$

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$$igtriangleup ABCsim igtriangleup XYZ$$

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

$$fracax=fracby=fraccz$$

Example

Find x in the similar triangles.

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We know that because the triangle are similar the sides room proportional which method that

$$fracx14=frac321Rightarrow$$

$$x=frac14cdot 321=frac4221=2$$

$$x=2$$

Video lesson

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