PPL NAV cockpit calculations

[Gertrude the Wombat]

If people really want to use "1 in 60" rules and suchlike they might, or might not (I might just be peculiar), want to remember where it comes from, which is simply that

sin x = x

to a reasonable approximation (ie as accurately as makes any difference to your flying) for small enough x. Where x is in radians of course, and one radian is roughly 60 degrees, so there you are.