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Help with a Geometry Problem - Calculating The Radius of a Curve

  1. Jun 5, 2012 #1
    Hello all

    I work in transport engineering. i have come across what seems to be a simple maths problem but i do not understand it.

    The problem relates to geometry i.e. calculating the radius of a curve using a chord and a versine.

    The problem is this:-

    " a general rule of thumb is as follows: with a chord length on 20m, the versine measured in mm (v) divided by 50000 gives the radius in meters (R) i.e. v=25mm -25/50000=2000-R=2000m"

    when i work this out i do not get 2000m. also the problem shows a -25 it could be a minus or just a dash i cannot be sure.

    Can anyone shed any light on this?

    Thank you for your help
     
  2. jcsd
  3. Jun 5, 2012 #2
    Well, your confusion is justified. It's an incoherent mess. None of those minus signs is a minus sign. Check the page www.mathopenref.com/arcradius.html and you should understand what is happening. Following the symbols used on that page, plug in a versed sine of H=25mm and a chord length of W=20m and you get the desired result of R=2000m.
     
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