This is a triangle. It has three sides. It has three angles. The sum of three angles of a triangle is 180. If three sides of a triangle are equal then the triangle is called isosceles.
This is a rectangle. I t has four sides . I t has four angles. The sum of its angles is 360. If four sides of a rectangle are equal then it is called a square. Each angle of square is of 90. Diagnoles of a square bisect each other.
This is a circle. It has a radius and a diameter. Diameter is 2 times the radius. Each radius of a circle is of equal length.