Question

I don't understand how:

*****The question is in the comments made by me I used the equation writer (SORRY)****

I assume there is a rule that is missing but which one?

----I commented below so you can see what it is supposed to look like with the equation writer.-----

Answer 1

.... wats dat?

Answer 2

you could use the whiteboard maybe

Answer 3

\[B _{2}\cos(\frac{ \pi n x }{ a })\]
and
\[B _{1}\sin(\frac{ \pi n x }{ a })\]
equal
\[Bsin(\frac{ \pi n }{ a } x + \frac{ \pi n }{ 2 })\]

Answer 4

hmmm.... is probably easier if ... you post a quick screenshot of it

Answer 5

maybe it's just me.... but can't see what it's meant to do

Answer 6

It says it is convenient to write both cases using a single formula.