Triangles is a closed figure with three straight sides and three angles. Those triangles which have exactly the same three sides and exactly the same three angles. If the figures have exactly the same shape and size are called congruent figures. The figures which are exactly the same in the shape but sizes may be different are known as similar figures.
The plane figure bounded by a curved line and every point of the line which is equidistance from a fixed point called the centre of the circle.The curved boundary line of a circle sis called its circumstance. The straight line is drawn from the centre of a circle to a point on its circumference is called the radius of the circle.