What is the difference between a line, a line segment and a ray?

In a circle of radius $r$ find the following:

Length of the diameter

In a circle of radius $r$find the following:

The two parts in which the diameter divides the circle

In a circle of radius $r$find the following:

The region enclosed between two radii and an arc

If three or more lines pass through the same point, then the lines are concurrent.

Only one line can be drawn from a point parallel to a given line.

The radii of all concentric circles are equal.

A triangle is a polygon having four sides.

A simple curve can be either opened or closed.