[G] Math Problem

Posted by Glen on Oct. 30, 2009, 3:21 p.m.

I need to build an arc that meets the height and width requirements, but first I need to know how long of a stick I'll be needing when I bend the wood. Help please?

Comments

Acid 15 years ago

About 45.06, if my math is right.

Inverse tangent of 8/13, about 31.608 degrees, converted to radians, about .552, and finally, multiplied by the circumference of a circle with a 26cm diameter, which gives you the answer.

Glen 15 years ago

Note that it's not part of a circle. Apparently that should be given. I received two answers so far on other sites. One being 33.91cm, and the other 33.46cm.

45cm is almost twice the width. Picturing that, it doesn't sound right.

Kenon 15 years ago

Hold it, is that half of an ellipse or what.

It depends on the inclination of the angle between the normal lines on the edges of the graph.

Assuming that is perfectly elliptical (Normal lines are the same), it would be half the size of the ellipse's perimeter of this, or around the values of 33.450955 cm to 33.4559 cm (Albeit the 33.4559 is probably more accurate as it is the estimation with an elliptic integral rather than the simplified perimeter of an ellipse function.)

But it all depends on "Is it half of an ellipse?". If it is not, you're screwed buddy.

Juju 15 years ago

The arc is half an ellipse, an 8x13 ellipse to be precise. The arc is therefore half a circumference. The best solution is:

2*pi( (a^1.5 + b^1.5)/2 )^(2/3)

Hence the arc length is:

pi( (13^1.5 + 8^1.5)/2)^(2/3)

= 33.45

Kenon 15 years ago

Not exactly Juju, remember that formula is good for an ESTIMATION (Which in this case is enough, but still).

Also you can only assume it is half of an ellipse, It COULD be an arc of another ellipse (Although that's really pushing it!)

Sorry, I'm a math nut.

Alert Games 15 years ago

This proves who the math nerd is around here…

Glen 15 years ago

I made the arc with 33.45cm. It fit perfectly.

Acid 15 years ago

LOL I thought circle instead of ellipse. >_< I feel dumb. :(

F1ak3r 15 years ago

Don't forget the animals, two of each.

Oh wait,

Quote:
arc

Nevermind.

Glen 15 years ago

lol Flak3r.