The formula for calculating length is:

We can also write

or

Why it does not matter?
Let's assume we have 2 numbers, a and b.
When we perform a subtraction:

, we get another number

When we perform another subtraction:

, we get a number

When we raise

or

to the power of 2, the result is the same,

.
No, it does not have a straight line. (A)
Answer:
vertical angles or opposite angles
Step-by-step explanation: