There are two ways to classify triangles: by sides, or by their angles.
Sides
A triangle is scalene if all of the sides are different lengths.
A triangle is isosceles if two of the sides are the same length, but the other side is a different length.
A triangle is equilateral if all three of the sides are the same length.
Angles
A right angled triangle is a triangle that has a right angle.
An obtuse angled triangle is a triangle that has one obtuse angle; the other two angles have to be acute.
An acute angled triangle is a triangle where all three of the angles are acute.
Vertically Opposite Angles
When you have two intersecting lines, the angles directly across from each other are the same. Thus, the angles are "vertically opposite".
Practice Questions
Page #
