Difference between revisions of User:Divenal/sandbox
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This combines the two ideas... It's sized to suit my smartphone, but feel free to make your custom version as above. | This combines the two ideas... It's sized to suit my smartphone, but feel free to make your custom version as above. | ||
<br clear="both" /> | |||
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[[File:TrigonometryTriangle.svg|right|TrigonometryTriangle]] | |||
A reminder about some trigonometry / geometry | |||
# <math>tan(A) = \frac{a}{b}</math> | |||
# for very small angles (expressed in radians), <math>tan(A) \approx A</math> | |||
# 1 radian = <math>\frac{180}{\pi}</math> degrees = <math>\frac{60 \times 180}{\pi}</math> arc-minutes | |||
"20/20" acuity is defined as the ability to resolve details which subtend 1 arc-minute at the eye. | |||
So if 'A' is 1 arc-minute and 'b' is the distance to the object, then the height 'a' of the object is | |||
is | |||
<math>a = \frac{60 \times 180}{pi} \times b = 0.00029 \times b</math> | |||