Question

Is there an aid for remembering SOHCAHTOA and is there a mnemonic device for the SI system?

Answer 1

SohCahToa IS the aid for remembering the basic trig functions.
Where o is the side opposite the angle in question (theta), a is the side adjacent and h is the hypotenuse:
\[\Large \begin{array}{l}
\sin \theta = \frac{o}{h}\\
\cos \theta = \frac{a}{h}\\
\tan \theta = \frac{o}{a}
\end{array}\]

Answer 2

What exactly do you mean the SI system, what are you trying to remember about it

Answer 3

I can't think of any SI system mnemonics - just remember the base units: kilogram, metre, second, Ampere, Kelvin, candela and mole. I suppose you could arrange this in some kind of easy-to-recall mnemonic:
k
m
s
A
K
c
m
But I've always just remembered the units themselves.