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.
In an equilateral triangle, all sides are the same length. An equilateral triangle is also a regular polygon with all angles 60Â°. In an isosceles triangle, at least two sides are equal in length. An isosceles triangle also has two equal angles: the angles opposite the two equal sides. In a scalene triangle, all sides and internal angles are different from one another. By internal angles. Triangles can also be classified according to their internal angles, measured here in degrees.