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Author Topic: Math problem?  (Read 4108 times)

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Brick_top

  • Guest
Math problem?
« on: January 21, 2011, 09:28:41 AM »
I know the distances from A to B and C to D.

How do I get the Angle E?

I'm very bad at math, sorry
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SOFITO_SOFT

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Re: Math problem?
« Reply #1 on: January 21, 2011, 10:00:36 AM »
tangent ( E ) =  DC / CA

arc tang ( E ) = ang E   ( IN RADIANS )

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Brick_top

  • Guest
Re: Math problem?
« Reply #2 on: January 21, 2011, 10:13:16 AM »
Hi there! thanks for your response!

I guess someone must have already written the tangent and arc tang in autolisp?

Sorry If i'm saying something stupid.

I'll do a search
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Brick_top

  • Guest
Re: Math problem?
« Reply #3 on: January 21, 2011, 10:17:10 AM »
atan is arc tang right?
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Brick_top

  • Guest
Re: Math problem?
« Reply #4 on: January 21, 2011, 10:29:58 AM »
Quote from: SOFITO_SOFT on January 21, 2011, 10:00:36 AM
tangent ( E ) =  DC / CA

arc tang ( E ) = ang E   ( IN RADIANS )



You have there Tangent (E) = DC / CA

But I don't know CA

I only know distances I don't know coordinates
« Last Edit: January 21, 2011, 10:48:17 AM by Brick_top »
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dgorsman

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Re: Math problem?
« Reply #5 on: January 21, 2011, 10:53:41 AM »
You know the lengths of two sides and there's a right angle.  Look to Pythagoras.
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Brick_top

  • Guest
Re: Math problem?
« Reply #6 on: January 21, 2011, 11:02:33 AM »
I know that when AB is rotated at the unknown angle E the distance between DC is met

In case I'm making any sense
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SEANT

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Re: Math problem?
« Reply #7 on: January 21, 2011, 11:13:17 AM »
I think you need ASIN(CD/AB).

That is if AD = AB, i.e., A at center of circle.
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Sean Tessier
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Guitar_Jones

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Re: Math problem?
« Reply #8 on: January 21, 2011, 11:15:33 AM »
Quote
But I don't know CA

Assuming A is at the center of your circle
RADIUS = AD = AB

If you must know AC, you can then use the pythagorean theorum as suggested.
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Brick_top

  • Guest
Re: Math problem?
« Reply #9 on: January 21, 2011, 11:21:13 AM »
Quote from: SEANT on January 21, 2011, 11:13:17 AM
I think you need ASIN(CD/AB).

That is if AD = AB, i.e., A at center of circle.

Hi there, thanks a lot  :-)

using this function I got from here: http://autocad.wikia.com/wiki/Asin_(AutoLISP_function)

Code: [Select]
;;;  WIKI-ASIN
; End AutoLISP comment mode if on |;
(DEFUN WIKI-ASIN (X)
;| Returns the arc sine of a number
   Edit the source code for this function at
  asin (AutoLISP function)
|;
 (ATAN X (SQRT (- 1 (* X X))))
)
worked fine
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CAB

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Re: Math problem?
« Reply #10 on: January 21, 2011, 12:54:35 PM »
« Last Edit: January 21, 2011, 12:58:24 PM by CAB »
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SOFITO_SOFT

  • Guest
Re: Math problem?
« Reply #11 on: January 21, 2011, 01:42:33 PM »
I know the distances from A to B = M
and C to D = N
How do I get the Angle E?
AD = AB  = M    <<<<   RADIOS OF CIRCLE
AC =  SQRT ( M^2 - N^2 ) = L <<< PITAGORAS
tangent ( E ) =  M / L
arc tang ( E ) = ang E   ( IN RADIANS )

in Alisp:
(( setq m ( distance a b ) )
( setq n ( distance c d ) )
( setq L ( sqrt ( - ( expt m 2 ) ( expt n 2 ) ) ) )
( setq e ( atan ( / n L  )) )
remember the swamp when you get to be like A. Einstein. :)
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dgorsman

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Re: Math problem?
« Reply #12 on: January 21, 2011, 01:43:14 PM »
All that high school math where you said "I'll never use this in the real world!" actually does have its uses   :-P
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If you are going to fly by the seat of your pants, expect friction burns.

try {GreatPower;}
   catch (notResponsible)
      {NextTime(PlanAhead);}
   finally
      {MasterBasics;}

SOFITO_SOFT

  • Guest
Re: Math problem?
« Reply #13 on: January 21, 2011, 01:44:02 PM »
Sorry:
tangent ( E ) =  N / L
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Lee Mac

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Re: Math problem?
« Reply #14 on: January 21, 2011, 05:09:30 PM »
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alanjt

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Re: Math problem?
« Reply #15 on: January 21, 2011, 09:31:34 PM »
Just remember: Some Old Hippie Caught Another Hippie Tripping On Acid

Some Old Hippie => Sine of opposite divided by hypotenuse => Sin (opp/hyp)
Caught Another Hippie => Cosine of adjacent divided by hypotenuse => cos (adj/hyp)
Tripping On Acid => Tangent of opposite divided by adjacent => tan (opp/adjacent)
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Brick_top

  • Guest
Re: Math problem?
« Reply #16 on: January 24, 2011, 04:01:43 AM »
Thanks a lot for all the help guys

alan that is very funny and useful, I'll keep it
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pkohut

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Re: Math problem?
« Reply #17 on: January 24, 2011, 04:12:00 AM »
Oscar Had - sin
A Hunk - cos
Of Ass - tan
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Kerry

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Re: Math problem?
« Reply #18 on: January 24, 2011, 05:04:16 AM »

 :-D

I guess you just made that up :)


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pkohut

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Re: Math problem?
« Reply #19 on: January 24, 2011, 05:37:47 AM »
Quote from: Kerry on January 24, 2011, 05:04:16 AM

 :-D

I guess you just made that up :)


Nope, Trig instructor. Said 80% of the trig we would ever need to know could be taught in less than 2 minutes.  Just had to memorize the quote.  :-D
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Brick_top

  • Guest
Re: Math problem?
« Reply #20 on: January 24, 2011, 06:38:30 AM »
Thanks for that one to :D
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