## Search found 5 matches

Tue Aug 19, 2014 11:26 pm UTC
Forum: Mathematics
Topic: Mathematical etymology coincidence?
Replies: 8
Views: 3654

### Mathematical etymology coincidence?

So I was playing around with the error function, aka erf(x), and I had always assumed that erf(x) was an abbreviation of "error function." But then, when I look at the E(erf(x)), I notice that erf'(x)=-x*erf(x) or y'=-xy. I realized then that solutions to that type ...
Mon Mar 17, 2014 12:21 am UTC
Forum: Mathematics
Topic: Bearing in a plane to contact in 3D space
Replies: 3
Views: 1686

### Re: Bearing in a plane to contact in 3D space

Thank you! I feel kinda stupid that the answer was a trig identity. But, I think you swapped numerator and denominator in the final equation. tan B = [cos(CA1)sin(H2)-cos(CA2)sin(H1)]/[cos(CA2)cos(H1)-cos(CA1)cos(H2)] Should be tan B = [cos(CA2)cos(H1)-cos(CA1)cos(H2)]/ [cos(CA1)sin(H2)-cos(CA2)sin(...
Fri Mar 14, 2014 6:53 pm UTC
Forum: Mathematics
Topic: Bearing in a plane to contact in 3D space
Replies: 3
Views: 1686

### Bearing in a plane to contact in 3D space

I'm trying to solve an equation based on the conical angle formula. If you have the conical angle to a target, how do you find out the bearing to it's projection onto a plane? I've taken the conical angle formula, for the angle between two vectors rotated around different, perpendicular axes, but I'...
Wed Sep 12, 2012 8:41 pm UTC
Forum: What If?
Topic: What-If 0011: "Droppings"
Replies: 68
Views: 32077

### Re: What-If 0011: Droppings

Surprised at his bit about unit conversions. Mostly because it's factually incorrect, and I tend to like him for being right on these things. :( "miles per gallon" is lazy notation we accept in speech. If you want to use it in math, you need to recognize it's "miles traveled per gall...
Tue Sep 11, 2012 10:07 pm UTC
Forum: What If?
Topic: What-If 0011: "Droppings"
Replies: 68
Views: 32077

### Re: What-If 0011: Droppings

I wrote a post but accidentally closed a page and don't have my steps. Summary: poops, like mouths, have a diameter. If we assume a round poop of 1 sq cm and a round mouth, the target area increases; expected wait time is now 123 years. Waiting for poop is a poisson process, and the wait time is exp...