Because they can be combined to form any polygon,
triangles are by far the most important polygon to
study. With a good base of knowledge of triangles, you can find out almost
anything about any polygon.

Every triangle has six main parts, its three sides and three angles. A triangle
can be classified by either of these criteria--sides or angles. In addition to
falling into a certain category based on sides or angles, triangles can also
qualify as special triangles by meeting more specific requirements. Special
triangles such as equilateral, isosceles, and right triangles, have
very precise properties and characteristics that help us draw conclusions about
unknown figures. In the following lessons, we'll take a look at some general
characteristics of all triangles, and then move to examine the characteristics
of special triangles.