This image is about 3 sided triangles and angles known as polygons. A 3 sided triangle can be Scalene that means it has no sides the same length ,  Isoceles is a triangle that has 2 sides the same length, and a Equalateral triangle has all sides the same  length. A 3 sided angle can be Acute less than 90 degrees, Right exactly 90 degrees, and Obtuse is more than 90 degrees.