Khan/khan-exercises — Issue #4738: Parabola intuition 3 - Parabola intuition 3 - calculation bug
Author: KhanBugz
Created: 2011-10-21 20:14:58+00:00
State: open
Labels: chrome

Reporter: eldadz@gmail.com

Hello,

it was quite suspicious that the directrix was on y=1000/1001 to begin with, so I checked the "hints", and the following calculation for "a" is showed as followed:

a = 1/(2 * (0 - 1000/1001)) = 0

Which is, of course, wrong.
It should have been -0.49950... (or better, if the directrix was y=1, -1/2).

I'm quite curious to that could cause such a thing.

[parabola_intuition_3.html?seed=163&problem=0](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/parabola_intuition_3.html?seed=163&problem=0&debug)

[["1/2","1/2","1/2","0.5","0","1"]]

Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/14.0.835.202 Safari/535.1

MathJax is loaded, ready, queue length: 0