Introduction to Euclid's Geometry — Question 2

We have to define some other terms like : Ray, Straight line and a Point.

Ray - A ray is a part of a line, that has a fixed starting point but no end point. It can extend infinitely in one direction.

Straight Line - A line that connects two points in a plane and extends to infinity in both directions. It is considered one dimensional figure.

Point - A small dot made by a sharp pencil on a sheet of paper gives an idea about a point. A point has no dimension i.e, length, breadth and height, it has only a position.

(i) If the perpendicular distance between two lines is constant, then these lines are considered parallel to each other.

(ii) If the angle between two lines is equal to 90°, then these lines are considered perpendicular to each other.

(iii) A part of a line that has two endpoints and is the shortest distance between them, is a line segment.

(iv) The distance from the center to any point on the circumference of the circle is called the radius of the circle.

(v) A square is a regular quadrilateral that has four equal sides and angle between each side is a right angle.