November 10, 2008

This resource has been contributed by Winpossible, and can also be accessed on their website by clicking here - Triangles Classification.

Here you'll learn with the help of diagram; video and explanation by instructor, in what ways triangles can be classified. Triangles are classified, or grouped, in two different ways. One classification distinguishes by the sides, and another by angles. For a triangle, you can have all three sides congruent (equal measure), or two sides congruent, or no sides congruent.

Let us learn about classification according to their sides: An equilateral triangle has all the sides and angles congruent to each other i.e. in triangle*ABC*, side *a* = *b* = *c* and m*A* = m*B* = m*C* = 60°. Isosceles triangles have two sides congruent, called the legs, and also two angles congruent, called the base angles. The non-congruent side is called the base i.e. in triangle *ABC*, *AB* and *AC* are legs and *BC* is the base, and angles *B* and *C* are base angles, side: *b* = *c* and m*B* = m*C* . It is noted that every equilateral triangle is an isosceles triangle, but not all isosceles triangles are equilateral triangles.

In scalene triangle, all sides are of different lengths and interior angles are all of different measures i.e. in triangle*ABC*, sides *a* ? *b* ? *c*, and m*A* ? m*B* ? m*C* .
When studying at classification by their angles: An acute triangle is a triangle with all three angles measuring less than 90° i.e. in triangle *ABC*, m*A* , m*B* , m*C* < 90°. An obtuse triangle is a triangle that has one angle with measure greater than 90°? e.g. in triangle *ABC*, m*B* > 90°?. In case of a right triangle it has one angle with measure of 90° e.g. in triangle BAC, m*A* = 90°. An Equiangular triangle is a triangle whose all angles are congruent i.e. in triangle *ABC*, m*A* = m*B* = m*C* = 60°. It may be noted and remembered for triangles classification by angle measure; that even though right triangles and obtuse triangles each have two acute angles, their classification is not affected by these angles. Acute triangles have all three acute angles.

Here you'll learn with the help of diagram; video and explanation by instructor, in what ways triangles can be classified. Triangles are classified, or grouped, in two different ways. One classification distinguishes by the sides, and another by angles. For a triangle, you can have all three sides congruent (equal measure), or two sides congruent, or no sides congruent.

Let us learn about classification according to their sides: An equilateral triangle has all the sides and angles congruent to each other i.e. in triangle

In scalene triangle, all sides are of different lengths and interior angles are all of different measures i.e. in triangle

This FREE mini-lesson is a part of Winpossible's online course that covers all topics within Geometry. Click on the video below to go through it. If you like it, you can buy our online course in Geometry by clicking here.

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