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Homework Help: Geometry problem

  1. Dec 21, 2011 #1
    1. The problem statement, all variables and given/known data
    Disparity is defined as [itex]\delta = \alpha - \beta[/itex]. Find [itex]\delta[/itex] in terms of interocular distance a, viewing distance D and d, e and f.

    http://img220.imageshack.us/img220/7576/43519392.jpg [Broken]

    3. The attempt at a solution

    I'm not getting anywhere. Any tips to get me started?
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Dec 21, 2011 #2
    I would start by writing down the tangent relations. For example, α is the difference between the two angles that Q and P make from the vertical (forward?) direction. So

    α = atan(f/(D+d)) - atan(e/D)

    and so forth.

  4. Dec 22, 2011 #3
    Thanks. Then:

    [itex]\beta = \arctan(\frac{a - e}{D}) - \arctan(\frac{a - f}{D + d})[/itex]

    Correct? Then I already have my answer it seems.
  5. Dec 22, 2011 #4
    Yes. It seems like you're about there. Don't forget the problem asks for δ=α-β.
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