# Thread: Simple - getting a common denominator

1. ## Simple - getting a common denominator

i have -$\displaystyle cosx/sin^2x + 1/sin^3x$

This is really elementary stuff i know... but i'm fairly sure these can be brought to a common denominator to add them properly. I just cannot for the life of me remember how to do it.

2. Originally Posted by NotEinstein
i have -$\displaystyle cosx/sin^2x + 1/sin^3x$

This is really elementary stuff i know... but i'm fairly sure these can be brought to a common denominator to add them properly. I just cannot for the life of me remember how to do it.
the "least" common denominator is $\displaystyle \sin^3 x$

both denominators can go into it. it is a multiple of both and since it is equal to one, it is the "smallest"

3. Originally Posted by Jhevon
the "least" common denominator is $\displaystyle \sin^3 x$

both denominators can go into it. it is a multiple of both and since it is equal to one, it is the "smallest"
so would it be...

$\displaystyle (-cosx)(sinx)/sin^3x + 1/sin^3x$ ?

4. Originally Posted by NotEinstein
so would it be...

$\displaystyle (-cosx)(sinx)/sin^3x + 1/sin^3x$ ?
and you say you're not Einstein! Pfft! yes, now add those two