Re: 1 in x versus %

[Eddie.Oliver@efs.mq.edu.au (Eddie Oliver)]

"Roderick Smith" <rodsmith@werple.net.au> wrote:

>
>Ton convert 1 in x to p%, divide x into 100.
>So: 1 in 50 is 2%; 1 in 100 is 1%; 1 in 12 is 8.3%.
>
>Likewise, to convert p% into 1 in x, divide p into 100.
>So: 1.5% = 1 in 67.

That's all very well as a straight conversion. The trouble is (as has been
indirectly noted in another thread) that there is not universal agreement as
to whether a grade figure represents the sine or the tangent of the angle of
inclination.

Often (e.g. in north america ) percentage figures  represent the tangent of
 the angle, while 1 in n grades represent the sine.

The fortunate thing is that for small theta, sin (theta) is very close to tan (theta),
so the difference is pretty trivial and probably irrelevant for the usual number
of significant figures. For steeper grades, it may be an issue.

If it is an issue, the conversion is simple by basic trigonometry.

Eddie Oliver