What is a Triangle?
• Measurements of Interior Angles • Sum of Interior Angles: Sample Problem • Sum of Interior Angles: Solution • Constructing a Triangle: Sample Problem • Types of Triangles by Sides • Types of Triangles by Angles • Isosceles and Equilateral Triangles • Relationship Between Sides and Angles • Calculating Area of a Triangle • Right Triangles • Right Triangle: Sample Problem • Two Right Triangles: First Solution • Two Right Triangles: Second Solution • Summary
Triangles are one of the fundamental figures used in Euclidean geometry. There are three elements required to make a triangle. It is a • 3-sided • plane or two-dimensional figure, in which • the sum of the interior angles equals exactly 180 degrees. There are two common systems of triangle classification. One focuses on the sides and designates three types of triangle. Equilateral Triangle. Equilateral means “equal sides,” and in an equilateral triangle, all three sides are the same length. This means that the angles will also be equal – all 60° – making the triangle equiangular as well. Isosceles Triangle. Isosceles means “equal legs,” and an isosceles triangle has two sides that are equal in length. This also means that the two angles formed where the equal sides meet the third side are equal. Scalene Triangle. Scalene comes from a word meaning “uneven,” and a scalene triangle has three unequal sides. As you might suspect, then, the three angles are unequal as well. The other triangl
