Geometry/Chapter 4/Lesson 1
Introduction[edit | edit source]
What is a triangle?[edit | edit source]
A triangle is a figure formed by 3 segments joining 3 noncollinear points. Each of these 3 points [in the triangle] are a vertex of the triangle. The segments are what is known as the sides of the triangle.
How do we classify triangles?[edit | edit source]
We can classify them by their angles or sides. This lesson we will go over how to classify triangles by their angles. Next lesson (Geometry/Chapter 4/Lesson 2), you will go over the 2nd way of classifying triangles: By their sides.
Classifying Triangles by Angles[edit | edit source]
One way of classifying triangles is by their angles. All triangles have at least 2 acute angles, but the third angle is used to classify what type of triangle it is.
- Acute Triangle
In an acute triangle, ALL of the angles are acute (<90). There is no single angle in this triangle that is (≥ 90).
- Obtuse Triangle
In an obtuse triangle, only ONE angle is obtuse. Only one angle in this triangle is (> 90).
- Right Triangle
In a right triangle, only ONE angle is right (= 90).
- Equiangular triangle
In an equiangular triangle, ALL angles are congruent (<1 = <2, <2 = <3, <1 = <3).