[DPRG] math I once knew
Subject: [DPRG] math I once knew
From: Sluggy!
slugmusk at linuxlegend.com
Date: Fri Dec 20 16:59:00 CST 2002
I knew it would be pretty simple and infact, I'd tried the very solution
as Kip presented it:
radius * sin(angle) = Y
radius * cos(angle) = X
For my example, I used a radius of 3" and using Excel, I calculated the
coordinates for each point along the clock face for the first 15 minutes.
There is, however, a problem with the numbers.
hour
min
radius
deg
X
Y
12
0
3
0
3
0
1 3 6 2.88051086 0.838246495
2 3 12 2.531561876 1.609718754
3 3 18 1.980950125 2.25296174
4 3 24 1.272537022 2.716735086
1
5
3
30
0.46275435
2.964094872
6 3 36 0.383891069 2.97533656
7 3 42 1.199955945 2.749564644
8 3 48 1.920433018 2.304763984
9 3 54 2.487929499 1.676367147
2
10
3
60
2.857238941
0.914431863
11 3 66 2.998942368 0.079653462
12 3 72 2.901751765 0.761470088
13 3 78 2.57340928 1.541935368
14 3 84 2.040070487 2.19957096
3
15
3
90
1.344220848
2.681989991
If you look at these, 0 degrees works out fine, corresponding to the 3
o'clock position as given. Then the points run clockwise from 3 o'clock
all the way to about 11 o'clock. I would have expected 90 degrees to end
up at 6 o'clock, with X = 0 and y = 3, but even the closest value (36
degrees) isn't exactly 6 o'clock.
The formulae in Excel are
X = radius * COS(deg)
Y = radius * SIN(deg)
with relative cell addresses rather than values, of course.
Any ideas what I'm skipping?
Sluggy!
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