TITLE: Notation for equivalent equations
QUESTION [5 upvotes]: What is the notation for showing that equations are equivalent by rearranging terms?
For example, for the arc length formula:
$$s=r\theta$$
I sometimes solve for $r$ and write it as
$$r=\frac{s}{\theta}$$
When I show my work, I usually write this relationship like this:
$$s=r\theta\Rightarrow r=\frac{s}{\theta}$$
Is this the correct way to write it or is there a better way? Up to this point, my teachers haven't cared, but I know in college and later in high school it will definitely matter.

REPLY [5 votes]: Per request by GamrCorps, I post my original comment here.
What you have written says that the truth of the expression on the left implies the truth of the expression on the right. It is correct. If you want equivalence you can use the double arrow that shows how the truth of either implies the truth of the other.