The most difficult mathematics is that which you do not know. A surprising amount of mathematics is actually easy once you've learned it. Of course, once you learn the easy stuff, then you have to start tacking the deep stuff, and that gets harder.
An isosceles triangle has two sides of equal length. An isosceles triangle also has two angles of the same measure; namely, the angles opposite to the two sides of the same length; this fact is the content of the isosceles triangle theorem, which was known by Euclid.
Isosceles Triangles. There are many types of triangles in the world of geometry. There is a special triangle called an isosceles triangle. In an isosceles triangle, the base angles have the same degree measure and are, as a result, equal. At the same time, if two angles of a triangle have equal measure, then the sides opposite the angles are the same length. The easiest way to define an isosceles triangle is that it has two equal sides.