Originally Posted by Piltdown Man
Reduce the whole thing to remembering three numbers: 0.5, 0.7 & 0.9. These numbers can be used as the sines/co-sines, as appropriate, for 30, 45 and 60 degrees. Use them as appropriate. They are accurate enough for government work.
Works a treat (for contract work as well!).
Framer, Hefield, 60° is 0.9, not 0.8.