## Types of Triangles Based Upon Internal Angle Measurements

Triangles can be categorized according to the their internal angles, described below using degrees of arc.

- Right Triangle (or right-angled
triangle): Possesses one 90° internal
angle (a right angle). The side opposite
to the right angle is the hypotenuse; it is the longest side in the right
triangle. The other two sides are the
*legs*of the triangle.

- Obtuse Triangle: Possesses one internal angle larger than 90° (an obtuse angle).

- Acute Triangle: Possesses internal angles that are all smaller than 90° (three acute angles). An equilateral triangle is an acute triangle, but not all acute triangles are equilateral triangles.

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