Triangles
Triangles are classified by the measures of their sides and angles. All triangles have three sides and three angles and the sum of the angles in any triangle always equals 180°.
An equilateral triangle has three equal sides and three equal angles. Each angle measures 60°. 60 + 60 + 60 = 180°
A right triangle is any triangle with a perfect 90° angle, also called a right angle. The longest side is always opposite the right angle and is called the hypotenuse. The two smaller angles will always equal 90° when added together. 90° + 90° = 180°
An isosceles triangle has at least two equal sides. The two angles opposite those sides are also equal.
A scalene triangle has no equal sides and no equal angles.
Can a triangle be classified as more than one kind? Yes! An isosceles triangle that has a right angle is also a right triangle. An equilateral triangle is also isosceles because it has at least two equal sides.
Take time to memorize the properties and definitions of the four kinds of triangles. Some geometry questions can be easily answered using these properties.
