It's a value you should probably memorize:

You can derive it using some trigonometric identities, other known values of cosine, and properties of the cosine function. For example, using the double angle identity for cosine:

If
, then

and you probably know that
, so

When we take the square root, we should take the positive root because
whenever
:

Addition: -9 + -2 = -11
Substraction: -9 - 2 = -11
Answer: a line segment has a start and end point. a ray has one starting point and goes on forever. a line has no start or stop. it just goes on forever. hope this helps!!!
Good luck!!!!!!!
Step-by-step explanation: