Answer: It is not clear what you are asking for when you say "fifth formula". There are many formulas in mathematics, and it could be referring to different things in different context.
Formulas can be found in different branches of mathematics and science, such as geometry, algebra, physics, chemistry, etc. Can you please provide more context or specify what area of mathematics or science you are interested in?
It is important to note that any formula needs to be referenced in order to understand what it represents and how to use it.
Explanation: