inverse sine grrrrrrrr

[twood1702]

I am having an issue. I need to input inverse sine in lisp. I have tries asin, asine, arcsin, arcsine...... What is the actual input for this or can you even do this. my mathmatic equation is

 

2 X inverse sine (9\2r)= degrees of rotation

 

in lisp (setq deg (* (inverse sine (/ (width) (* 2 radius))) 2))

 

What do I put instead of the inverse sine?

[PS_Port]

 
;;; arcsine (inverse sine) accepts an argument in the range
;;; -1.0 to 1.0 inclusive, and returns an angle in radians in
;;; the range (-pi/2) to (pi/2) inclusive.
(defun asin (z /)
(atan z (sqrt (- 1.0 (* z z))))
)

[twood1702]

no workey.... or just me.

here is what I put in now

 

I am entering 5784 for radius

108 for width

 

(defun c:rpark ()
(defun asin (z /)
(atan z (sqrt (- 1.0 (* z z))))
 )
(setq r1 (getreal "\nEnter radius of arc in inches: "))
(setq w1 (getreal "\nEnter width of parking spaces in inches: "))
 (setq deg (* (asin (/ w1 (* 2 r1)))2))
)

 

When running this it returns 0.0186725

 

my hand math (which may be sketchy too:D )

r1 * 2 = 11568

w1 \ 11568 = .009336

arcsine of .009336 = 0.53

0.53 * 2 = 1.07

 

Drawing this out I have found my math to maybe correct, (please let me know if not:roll: )

 

soooo something seems to be amiss

[PS_Port]

Can you give a sketch or screen shot of what you are trying to accomplish..

looks like automatic parking bay setout ??

[CarlB]

Here's one from Bill Kramer:

 

;Inverse Sine Arcsin(X) = Atn(X / Sqr(-X * X + 1)) 
;
(defun arcsin (sn)
  (cond
    ((> (abs sn) 1.0) (prompt " Arc-sine error."))
    ((equal (abs sn) 1.0 0.000000001)
       (* sn (/ pi 2)))
    ((zerop sn)
       0.0)
    (t
       (atan (/ sn (sqrt (- 1 (* sn sn))))))))

[twood1702]

Can you give a sketch or screen shot of what you are trying to accomplish..

looks like automatic parking bay setout ??

 

 

That is exactly what I am trying to do. I want to automatically layout parking along a radius with a set width for the bay. Do you have something already? Sorry I don't have a screen shot of what I am trying.

 

This thing is going to test me, as I am just returning to writing lisp after a 6 year layoff from writing them. I was doing structural drawings when I was last at it. Now architectural, so I have new needs.

[twood1702]

(defun c:rpark ()
(defun arcsin (sn)
  (cond
    ((> (abs sn) 1.0) (prompt " Arc-sine error."))
    ((equal (abs sn) 1.0 0.000000001)
       (* sn (/ pi 2)))
    ((zerop sn)
       0.0)
    (t
       (atan (/ sn (sqrt (- 1 (* sn sn))))))))
(setq r1 (getreal "\nEnter radius of arc in inches: "))
(setq w1 (getreal "\nEnter width of parking spaces in inches: "))
 (setq deg (* (arcsin (/ w1 (* 2 r1)))2))
)

 

same as before 0.0186725.........I must not be understanding something.....arcsine and inverse sine are the same thing right? The number I need to get to when using the 5784 and 108 should come up to 1.07 degrees of rotation.

 

 

I'm so frustrated. I have been at this all day!!!

[PS_Port]

Sorry twood I dont have something,

just the long hand way..

try CarlB's let us know how it goes,

[CarlB]

Lisp uses angles in radians. If you want answer in degrees, multiply by 180/pi and you'll have it.

[PS_Port]

Why are you doubling the radius..

 

The radius is basically the hypotenuse ?

[PS_Port]

On the ball Carlo:)

[twood1702]

Yeah I knew that! Sorry, not a math genius here. I just didn't know where to go after what I had started. Thanks for all the help!!!!

[twood1702]

ahhh got it fianlly on Wednesday! If anyone is interrested in having something like this, let me know and I can give you the code. It's very nice to layout parking along a radius at user set widths of parking!