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radius of a given chord question

bhigdog

Stainless
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Jul 20, 2005
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Eastern PA
Help for math dummy please:
Given a chord of 3.000" and .250" perpendicular from the center of the circle arc to the chord. What is the radius of the circle. If there is something in da book I can't find it. ............Bob
 
Please excuse my ignorance of high school geometry, but don't the two ends of a cord intersect the circle so that the radius is the hypotenuse of the right triangle formed by the perpendicular and half the cord?
r = sqrt( 1.5^2 + 0.25^2 ) = 1.52
 
Please excuse my ignorance of high school geometry, but don't the two ends of a cord intersect the circle so that the radius is the hypotenuse of the right triangle formed by the perpendicular and half the cord?
r = sqrt( 1.5^2 + 0.25^2 ) = 1.52

It's worded a little funny in the OP, but he means from the cord to the center of the arc segment bounded by it. Like a tangent line shifted .25" towards center makes a cord of 3"
 
Yeah, thanks i just realized that's what the op meant. In that case ,
r = ( .25^2 + 1.5^2 ) / ( 2 × .25 ) = 4.625
 
You guys are making my head hurt but I'm glad you're here for me. R = 4.625 it is. Now I've got to generate something close to that on a manual lathe.........Bob
 
That or make a template. Doesn't need to be close. Just a once and done die to dish a .093 mild steel disc. Thanks...Bob
 
My Grandpa worked for GE over at Nela Park in Cleveland. He left me some of his old books and one of them had a bunch of useful formulas, including finding a chord of a circle given a known radius. I suck at algebra so I turned it into a Python script. It will ask if you want the chord, height or radius, and then give the answer.
Just download the text file and save it as a .py file.
 

Attachments

  • chord_calc.txt
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Python? I would rather figure out how to use a slide rule instead.

This is hardly even a trig problem except knowing the Pythagorean theorem. Draw a diagram and apply a little algebra. It took about a minute to derive a general symbolic answer once i understood the question. I feel sorry for the people that lack basic mathematical (as seperate from arithmetic) skills in the same way as i feel sorry for the illiterate.
 
Python? I would rather figure out how to use a slide rule instead.

This is hardly even a trig problem except knowing the Pythagorean theorem. Draw a diagram and apply a little algebra. It took about a minute to derive a general symbolic answer once i understood the question. I feel sorry for the people that lack basic mathematical (as seperate from arithmetic) skills in the same way as i feel sorry for the illiterate.

At the risk of appearing thin skinned, which I generally am not, please do not feel sorry for me and my lack of mathematical skills. To compensate for that I have developed the ability seek out others who do have the skills
I need to help solve my life's questions and problems. This has enabled me to become moderately wealthy and quite contented with my lot.
Your answer to my problem was incorrect.
Always remember, the first rule of any problem is R.T.F.Q (Read the fucking question).
BTW, as for your literacy, you misspelled separate..... Sorry.... Cheers.....Bob
 
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