Ringadon February 26, 2009 Share Ringadon Member February 26, 2009 (edited) I"m pulling an all-nighter tonight to finish up a project and I can't remember an equation that I need. if you take a right triangle base and draw an arc between the two legs at their ends how do you find the length of the arc. in my case (and in the example provided) I have x = 5 and y = 3 and I'm trying to find z might want to note that the numbers provided are arbitrary and I'm trying to get this info so I can better make a scale replica of a roll top desk. Edited February 26, 2009 by Ringadon Quote Link to comment Share on other sites More sharing options...
bushwack February 26, 2009 Share bushwack Member February 26, 2009 Looks like a quarter of a circle. http://www.mathgoodies.com/lessons/vol2/circumference.html I just got up too so this is all I have. Quote Link to comment Share on other sites More sharing options...
dragonfly February 26, 2009 Share dragonfly Member February 26, 2009 I dont think that's a circle, if x and y are perpendicular... I can show you arc-length on a circle (that's just gr.12 math) but I forget for an ellipse. Google it? Or maybe go here. Quote Link to comment Share on other sites More sharing options...
bushwack February 26, 2009 Share bushwack Member February 26, 2009 I was thinking he just needs a basic number to get started, what you gave him will make his head explode. Quote Link to comment Share on other sites More sharing options...
stutters February 26, 2009 Share stutters GC Alumni February 26, 2009 is it a geocities page? sure. am i pretty certain it's the right approach? definitely maybe. http://ca.geocities.com/web_sketches/ellip...arc_length.html Quote Link to comment Share on other sites More sharing options...
Ringadon February 26, 2009 Author Share Ringadon Member February 26, 2009 (edited) in quick answer to the questions asked <xy is a right angle/ x and y are perpendicular/ the exterior angle of xy is 270 I'm looking for the equation that spits out the arc length of z Also, it no longer really matters but now I want to know for future reference Ring Edited February 26, 2009 by Ringadon Quote Link to comment Share on other sites More sharing options...
boiler February 26, 2009 Share boiler Member February 26, 2009 Also, it no longer really matters but now I want to know for future reference I'm translating this as "The project was due an hour ago, so I'm hosed since no one came up with the answer in the middle of the night. But thanks for playing, guys." If you had asked this question 4 years ago, I might have been able to help you. Sorry. Quote Link to comment Share on other sites More sharing options...
Shropshire Slasher February 26, 2009 Share Shropshire Slasher Member February 26, 2009 K. Not knowing what course this is for or the nature of the assignment, I'll just offer the following: Stutters link is on the right path. Your problem involves the arc length of a space curve. In this case, the best way to proceed is to express your (assumed) elliptical arc in parametric form: x(t) = 5*cos(t), y(t)=3*sin(t). Now, form the derivatives x'(t)=dx/dt=5*sin(t) and y'(t)=dy/dt=-3*cos(t). Now, compute the arclength by the definite integral of dt over the range [0,2*Pi]. The integrand for the integral is SQRT[x'^2+y'^2]. This will yield the full perimeter of the ellipse, now divide by 4. Alternately, limit your range to [0,Pi/2]. Problem is, you end up with an Elliptical Integral of the Second Kind. The evaluation of which is an infinite series. See http://mathworld.wolfram.com/CompleteEllip...SecondKind.html Not sure what your instructor intended for you here. Other than not to try and do it at 12:58 the night before it was due. Quote Link to comment Share on other sites More sharing options...
NOFX February 26, 2009 Share NOFX Member February 26, 2009 god I hate that kind of math... crap like that is no fun and I find it to be frustrating. Discrete math and logic I am good at. says the software engineer Quote Link to comment Share on other sites More sharing options...
dragonfly February 26, 2009 Share dragonfly Member February 26, 2009 Shrop, yeah, that's what wiki said too Quote Link to comment Share on other sites More sharing options...
Ringadon February 26, 2009 Author Share Ringadon Member February 26, 2009 Also, it no longer really matters but now I want to know for future reference I'm translating this as "The project was due an hour ago, so I'm hosed since no one came up with the answer in the middle of the night. But thanks for playing, guys." Actually quite the opposite. I turned it in about 2 hours ago with the item I was asking the question about finished. The reason I posted it in the first place was because I was massively sleep deprived and couldn't think of what I needed. I ended up using trial and error to figure out how large I needed the roll part of my roll top desk to be. Thanks to everyone helping out. Even though I figured it out in a way that was really pretty easy I always like to know the math in doing things. Ring Quote Link to comment Share on other sites More sharing options...
Shropshire Slasher February 26, 2009 Share Shropshire Slasher Member February 26, 2009 Actually quite the opposite. I turned it in about 2 hours ago with the item I was asking the question about finished. The reason I posted it in the first place was because I was massively sleep deprived and couldn't think of what I needed. I ended up using trial and error to figure out how large I needed the roll part of my roll top desk to be. Thanks to everyone helping out. Even though I figured it out in a way that was really pretty easy I always like to know the math in doing things. Ring Shop class? Cuz if this was for Woods 101, then you shoulda just taken a piece of string, laid it on your template, then stretched it across your tape measure. You made me bust out Mathematica. Goof. Quote Link to comment Share on other sites More sharing options...
Ringadon February 26, 2009 Author Share Ringadon Member February 26, 2009 Actually quite the opposite. I turned it in about 2 hours ago with the item I was asking the question about finished. The reason I posted it in the first place was because I was massively sleep deprived and couldn't think of what I needed. I ended up using trial and error to figure out how large I needed the roll part of my roll top desk to be. Thanks to everyone helping out. Even though I figured it out in a way that was really pretty easy I always like to know the math in doing things. Ring Shop class? Cuz if this was for Woods 101, then you shoulda just taken a piece of string, laid it on your template, then stretched it across your tape measure. You made me bust out Mathematica. Goof. Actually, Theatre Design Seminar. Building 1/4 scale models of set pieces with nothing to actually base anything off of but the picture in our heads. (I had to draft out the ground plan and then create the pieces to put in it. all in all about a 12 hour job - the reading and re-reading of the play) I eventually ended up making something that seemed a little big to me but should also be able to hide an entire person in (which was kind of the idea when you're designing the set for a production of The Front Page. Besides, when a person is interested in learning it shouldn't be begrudgingly provided. Ring Quote Link to comment Share on other sites More sharing options...
dragonfly February 27, 2009 Share dragonfly Member February 27, 2009 If it takes one guy 6 days to do one job, and one guy 7 days to do one job, how long does it take both of them working together to do one job? Quote Link to comment Share on other sites More sharing options...
bushwack February 27, 2009 Share bushwack Member February 27, 2009 If it takes one guy 6 days to do one job, and one guy 7 days to do one job, how long does it take both of them working together to do one job? Is the job putting in a light bulb? Then it depends which one is holding the stool. Quote Link to comment Share on other sites More sharing options...
Shropshire Slasher February 27, 2009 Share Shropshire Slasher Member February 27, 2009 If it takes one guy 6 days to do one job, and one guy 7 days to do one job, how long does it take both of them working together to do one job? 13/42 days or 3.23077 days or 3 days, 5 hours, 32 minutes, 18.462 seconds. neglecting special relativity. Quote Link to comment Share on other sites More sharing options...
dwEEziL February 27, 2009 Share dwEEziL Member February 27, 2009 If 3 guys can dig 3 holes in 3 days, how many holes can one guy dig in half a day? Quote Link to comment Share on other sites More sharing options...
Ringadon February 27, 2009 Author Share Ringadon Member February 27, 2009 If 3 guys can dig 3 holes in 3 days, how many holes can one guy dig in half a day? none, the other 2 guys had the shovels Quote Link to comment Share on other sites More sharing options...
samurai nightling February 27, 2009 Share samurai nightling Member February 27, 2009 If 3 guys can dig 3 holes in 3 days, how many holes can one guy dig in half a day? 0.166666 of a hole. Quote Link to comment Share on other sites More sharing options...
shaftiel February 27, 2009 Share shaftiel Member February 27, 2009 If 3 guys can dig 3 holes in 3 days, how many holes can one guy dig in half a day? 0.166666 of a hole. Isn't that still one hole? never said how deep a hole it had to be did he? Shaftiel Quote Link to comment Share on other sites More sharing options...
Unclean February 27, 2009 Share Unclean Member February 27, 2009 0.166666 of a hole. Isn't that still one hole? never said how deep a hole it had to be did he? Same thing as dragonfly's question - we don't know enough about the "job". Is it something that can be divided amongst workers? If it takes 1 woman 9 months to have a baby, how long would it take 9 women? Quote Link to comment Share on other sites More sharing options...
dragonfly February 28, 2009 Share dragonfly Member February 28, 2009 (edited) Shrop wins If a number is assigned to each letter of the alphabet such that a=1, b=2, ... etc, then what is the product of the following: ( t - a )( t - B )( t - c )...( t - z )? If you can't do this in your head you suck at math. You don't need a calculator, just think about it logically. Edited March 2, 2009 by dragonfly Quote Link to comment Share on other sites More sharing options...
bushwack February 28, 2009 Share bushwack Member February 28, 2009 Shrop wins If a number is assigned to each letter of the alphabet such that a=1, b=2, ... etc, then what is the product of the following: ( t - a )( t - B )( t - c )...( t - z )? If you can't do this in your head you suck at math. I have my doubts. If if a man takes 1 minute to put in a light bulb how long would it take 100 men to put in the same light bulb? Quote Link to comment Share on other sites More sharing options...
dragonfly February 28, 2009 Share dragonfly Member February 28, 2009 (edited) Shrop wins If a number is assigned to each letter of the alphabet such that a=1, b=2, ... etc, then what is the product of the following: ( t - a )( t - B )( t - c )...( t - z )? If you can't do this in your head you suck at math. I have my doubts. If if a man takes 1 minute to put in a light bulb how long would it take 100 men to put in the same light bulb? Oh, that's easy. They're outside so they don't need a light bulb. Bush bush bush. Though, mine has an answer that's easier than most think. Doesn't even involve a complicated formula. Edited February 28, 2009 by dragonfly Quote Link to comment Share on other sites More sharing options...
dwEEziL February 28, 2009 Share dwEEziL Member February 28, 2009 If 3 guys can dig 3 holes in 3 days, how many holes can one guy dig in half a day? 0.166666 of a hole. Isn't that still one hole? never said how deep a hole it had to be did he? Shaftiel Shaft is right. Usually people say "Half a hole". No such thing as half a hole, just a smaller hole. Quote Link to comment Share on other sites More sharing options...
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