Types of Triangles
Scalene Triangle: no congruent sides;
Isosceles Triangle: only two congruent sides;
Equilateral Triangle: three congruent sides.
Right Triangle: one right angle (angle that measures 90º);
Acute Triangle: three acute angles (angles that measure less than 90°);
Obtuse Triangle: one obtuse angle (angle that measures more than 90º).
Height
The height of a triangle is the distance from a vertex to the oposite side. In the following figure, "h" is the height as measured from vertex A to side BC (h is a line segment perpendicular to side BC):
Every triangle has three heights.
Median
Median is a segment joining a vertex to the midpoint of the opposite side. Every triangle has three medians.
In the figure below, "m" is a median that joins vertex A to the midpoint (M) of side BC:
Internal Bisector
An internal bisector is a segment joining a vertex to the opposite side, dividing the internal angle in half.
In the figure below, "b" is an internal bisector that divides angle "A" in two congruent angles "a" (a = A/2):
External Bisector
An external bisector is a segment joining a vertex to the extension of the opposite side, dividing the external angle in half.
In the figure below, "b" is a bisector that divides external angle "A" in two congruent angles:
Congruent Triangles
Two triangles are congruent if, and only if, they have the same three sides and the same three angles.
Solved SAT Practice Tests
Find Practice Tests in the following links:
SAT Practice Tests - Triangles - Definitions
Additional Practice Tests - Triangles - Definitions
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