maybe
opposite rays have common end points
Is it true
no. A segment is a line with end points. Rays start in one place and go on forever.
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.
Yes, the definition of an angle is The amount of turn between two straight lines that have a common end point (the vertex). You can think of the arms as the two rays.
Gamma rays are at the end of the spectrum
all it is, is two rays in the same line that end with the same endpoint
They are at the end points of its diagonals
angle
An angle is formed between the two rays at the common end point.
A line?