# Unit 3: Triangles

## 19 terms

### vertex

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

### equilateral triangle

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

### right triangle

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

### obtuse triangle

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

### acute triangle

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

### isosceles triangle

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

### scalene triangle

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

### hypotenuse

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

### leg (right triangle)

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

### base

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

### leg (isosceles triangle)

The two sides of an isosceles triangle that are congruent.

### equiangular triangle

A triangle in which the three angles are congruent.

Sides of a triangle that share a vertex.

### opposite side

The side across from an angle.

### triangle

A polygon with three sides.

### vertex angle

The angle opposite the base of an isosceles triangle.

### 180 degrees

The sum of the interior angles of a triangle.

### base angles

The angles opposite the congruent sides of an isosceles triangle.

### congruent triangles

Two triangles that are have the same shape and size.