Equations

[afisher]

Is there a way to use equations in AutoCAD when drafting lines, arcs, offset, etc?  For example, I have a line which is 4".  I want to draw a line which is 1/3 of that known length.  Rather than calculating it on a calculator then coming back to AutoCAD, can it be done in AutoCAD?  Of course it would be nice if I could just type it into the input.

[pendean · Accepted solution]

Start HELP in AutoCAD and in the search box type:

Use the Command Prompt Calculator

[GrantsPirate · Accepted solution]

At the command line type
(/ 4.0 3)
Notice the 4.0 and not 4, otherwise you will get a rounded answer.
Multiply would be
(* 4.0 3)
as an example

[afisher]

Dean and GrantsPirate,

Both of these methods will be very useful.  They both require one extra step to initiate than I was anticipating, but is still better than picking up a calculator.

[dany_rochefort]

Hey bro, i was in a good mood so I wrote you a Lisp command that will do the work for you. It's not too sophisticated but it will do the job just fine.

Hopefully you know how to load a Lisp command ?!   Once loaded, you can invoke to command using XX on the keyboard.

(defun c:xx (/ len)

(princ "\nDividing Length by 1/3")
(setq len (getdist "\nEnter a length or pick points:       "))
(/ len 3)
)

;Dany Rochefort

; August 28th,2015
; Québec City Canada

Send some Kudos my way if it works out for you... Cheers

[GrantsPirate]

Just to clarify my solution, start the line command, pick a point, pull you cursor the direction you want to go, then (/ 4.0 3), enter.

And for multiplication the .0 isn't needed, just for division.  (* 4 3)

[dany_rochefort]

Totally agree with you, i wouldnt call those Solutions either. Using a personal calculator is quicker then writing algebriac notation a the command prompt.

[afisher]

Dany,

It looks like your lisp routine is only for 1/3.  Is this true?

[dany_rochefort]

Yes, 1/3 of the known length...

[dany_rochefort]

But you can modify it to anything you like...

Here is one for 1/4

(defun c:yy (/ len)

(princ "\nDividing Length by 1/4")
(setq len (getdist "\nEnter a length or pick points:       "))
(/ len 4)
)

Invoke command using YY at the keyboard...

[Kent1Cooper]

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@Anonymous wrote:

Is there a way to use equations in AutoCAD when drafting lines, arcs, offset, etc?  For example, I have a line which is 4".  I want to draw a line which is 1/3 of that known length.  ....

---

In the case of something as simple as a ratio of integers, you can do without the AutoLisp division (/)  function, because AutoCAD recognizes fractions of any numerator/denominator relationship [as long as they're both whole numbers] -- i.e. the numerator can even be larger than the denominator, and it will still know what you're talking about.  You can just pick a start point, aim the cursor in the direction you want to go, and type

4/3

And you don't even need to ensure that one of them is a real number [the 4.0 in Post 3 et al] -- in fact you can't, because it won't recognize it as a fraction that way.

[dany_rochefort]

This one will divide your known length by anything you want. Use ZZ to invoke with the keyboard.

(defun c:ZZ( / AA BB)
(setq AA (getdist "ENTER KNOWN LENGTH "))
(setq BB (getreal "DIVIDE SEGMENT BY ? "))
(setq CC (/ AA BB))
)

[GrantsPirate]

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@Kent1Cooper wrote:

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@Anonymous wrote:

Is there a way to use equations in AutoCAD when drafting lines, arcs, offset, etc?  For example, I have a line which is 4".  I want to draw a line which is 1/3 of that known length.  ....

---

In the case of something as simple as a ratio of integers, you can do without the AutoLisp division (/)  function, because AutoCAD recognizes fractions of any numerator/denominator relationship [as long as they're both whole numbers] -- i.e. the numerator can even be larger than the denominator, and it will still know what you're talking about.  You can just pick a start point, aim the cursor in the direction you want to go, and type

4/3

And you don't even need to ensure that one of them is a real number [the 4.0 in Post 3 et al] -- in fact you can't, because it won't recognize it as a fraction that way.

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In the case of 12.2 / 2.5 you would need to enter as 122/25 as decimals won't work in this manner.