Which pair of undefined terms is used to define a ray?

The undefined terms which are used to define a ray is:

Point and a line.

Step-by-step explanation:

The undefined terms in coordinate geometry are:

Line, Points and Plane.

since a line do not have any length, Point has a location but no size.

A line has no width and it extends infinitely and is one dimensional.

and a plane extends infinitely in both the dimensions.

Ray:

A ray is part of a line, has one fixed endpoint, and extends infinitely along the line from the endpoint.

Hence, the undefined terms which are used to define a ray is:

Point and a line.

1/5^2 = 7.56/45