2
One
An angle separates a plane to 3 sets: 1) Points between the 2 rays 2) Points on one of the rays 3) Points outside of the 2 rays
14
They have one point in common.
Just one.
Two and only two rays having the same end points are in an angle.
if the rays have no common points, the answer is zero. if the rays all have the same end point, the answer is 21 -- counting only the acute angles.
One! That is what collinear means!
Geometry teaches points, lines, rays, chords and segments.
Infinitely many. There an infinite number of points on a line and each point can be an end point of two rays.
A lens has two focal points -- one on each side of the lens. These focal points are where parallel rays of light converge after passing through the lens.
One