Understanding Triangles: Definitions, Types, and Properties

1. Defining Triangles During this lesson, you will define triangles and their parts.

2. ∆ w/ exactly one right (90 degree) angle ∆ w/ all angles measuring < 90 degrees ∆ w/ exactly one angle measuring > 90 ∆ w/ no sides equal in measure ∆ w/ at least 2sides equal in measure ∆ w/ all sides congruent Segment of a ∆ which connects the vertex of one angle w/ the mid- point of the opposite side Perpendicular segment in a ∆ from a vertex to its opposite side

3. Isosceles Triangle Parts In an isosceles triangle, the angle between the two sides of equal length is called ________________________________. The side opposite the vertex angle is called the _________ of the isosceles triangle. The two sides of equal length are called the ____________. The two angles opposite the two sides of equal length are called the ____________ of the isosceles triangle. vertex leg leg Base angles Base

4. Final Checks for Understanding • Triangles can be classified by ____________________________. • True or False. Explain. An equilateral triangle is isosceles. • Name (and describe) the ways in which we classify triangles by the lengths of their sides. • Name (and describe) the ways in which we classify triangles by the measures of their angles.