I always found these mnemonics just as hard to remember as the actual values so I just draw an isosceles right triangle and an equilateral one. It gives you the values for 30, 45 and 60 degrees.

My trick for this was:

0  30  45  60  90 deg
---------------------------
0  1   2   3   4

Sine function of the top equals half the square root of the bottom number. Cosine is just in reverse order.

I’m not sure I understand your mnemonic. It looks like you’ve got 1/sqrt(3) as one of your exact value for sine and cosine… but that surely isn’t right.