Bogus Solution
by b-flat, Jun 17, 2006, 3:21 PM
I have written a solution to find the volume of intersection of two cylinders that have radii of 1 and are perpendicular to each other. What is wrong with it
?
Look at the cube that contains the intersection. The probability of landing in each of the cylinders is
. Multiply them together to get the probability of landing in both cylinders:
. This is the area of the intersection over the area of the cube (which is 8), so shouldn't the volume of the intersection be
?
I'm amused that Saturday, I thought that that was the correct solution

reason it does not work

Look at the cube that contains the intersection. The probability of landing in each of the cylinders is



I'm amused that Saturday, I thought that that was the correct solution


reason it does not work
The cylinders are not independent of each other, so you can not just multiply together the probabilities of landing in each to get the probability of landing in both.
This brings me to a new question, how can you tell imediately in geometric figures if things are independent or dependent?
This brings me to a new question, how can you tell imediately in geometric figures if things are independent or dependent?