$(\frac{f}{g})' = \frac{gf' - fg'}{g^2}$ \hfill
$(fg)'= f'g + fg'$
$(x^n)' = nx^{n-1}$ \hfil $(sin(x))' = cos(x)$ \hfil $(cos(x))' = -sin(x)$
from the unit circle: $sin^2(x) + cos^2(x) = 1$
from the graph: $sin(x + \frac{\pi}{2}) = cos(x)$, "" " " $cos(x - \frac{\pi}{2}) = sin(x)$
Optional: $sin(-x) = -sin(x)$, \hfil $cos(-x) = cos(x)$