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vertex

The point where both rays (sides) of an angle meet.

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equilateral triangle

A triangle in which all sides are the same length and all angles are the same size.

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right triangle

A triangle that has a right angle. (90 degree angle)

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obtuse triangle

A triangle in which one angle is larger than 90 degrees.

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acute triangle

A triangle in which all three angles are less than 90 degrees.

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isosceles triangle

A triangle in which two sides are the same length and the two base angles have the same measure.

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scalene triangle

A triangle in which no two sides are of the same length.

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hypotenuse

The longest side of a right triangle, opposite the right angle.

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leg (right triangle)

The two sides of a right triangle that form the right angle.

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base

The third side of an isosceles triangle, it may not be congruent to the other two sides.

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leg (isosceles triangle)

The two sides of an isosceles triangle that are congruent.

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equiangular triangle

A triangle in which the three angles are congruent.

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adjacent sides

Sides of a triangle that share a vertex.

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opposite side

The side across from an angle.

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triangle

A polygon with three sides.

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vertex angle

The angle opposite the base of an isosceles triangle.

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180 degrees

The sum of the interior angles of a triangle.

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base angles

The angles opposite the congruent sides of an isosceles triangle.

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congruent triangles

Two triangles that are have the same shape and size.

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