已知夹角余弦，怎么用LISP求角度？

Lisphk

已知夹角余弦，怎么用LISP求角度？

newer

sin(x)^2+cos(x) ^2=1
cos(x)=a

sin(x)^2=1-a^2
sin(x)=(sqrt (1-a^2))

tan(x)=(/ (sqrt (1- (* a a))) a)
x=(atan (/ (sqrt (- 1 (* a a))) a))

evayleung

角度应该有两个值的吧。sin(x)=正负(sqrt (1-a^2))

cy956

doslib 9.0

dos_acos    (dos_acos number)     ■计算反余弦角度
number在[-1, 1]范围内.
返回：成功则返回反余弦角度值[0, π]，出错 nil .
示例:
(dos_acos 0.0)  -->  1.5708
(dos_acos 1.0)  -->  0

Free-Lancer

http://www.xdcad.net/forum/forum.php?mod=viewthread&tid=84321

牢固

1. ;;;acos 反余弦
   
2. ;; Args: -1 <= x <= 1;; By Lee Mac
   
3. (defun acos (x)
   
4.   (cond
   
5.     ( (< 1.0 (abs x)) nil)
   
6.     ( (equal (abs x) 1.0 1e-8) (/ pi 2.))
   
7.     ( (atan (sqrt (- 1.0 (* x x))) x))
   
8.   )
   
9. )
   
10. 
    
11. ;;;asin 反正弦
    
12. ;; Args: -1 <= x <= 1
    
13. ;; By Lee Mac
    
14. (defun asin (x)
    
15.   (cond
    
16.     ( (< 1.0 (abs x)) nil)
    
17.     ( (equal (abs x) 1.0 1e-8) (* x pi 0.5))
    
18.     ( (atan x (sqrt (- 1.0 (* x x)))))
    
19.   )
    
20. )
    

;;;acos 反余弦<br /> ;; Args: -1 <= x <= 1;; By Lee Mac<br /> (defun acos (x)<br />   (cond<br />     ( (< 1.0 (abs x)) nil)<br />     ( (equal (abs x) 1.0 1e-8) (/ pi 2.))<br />     ( (atan (sqrt (- 1.0 (* x x))) x))<br />   )<br /> )<br /> <br /> ;;;asin 反正弦<br /> ;; Args: -1 <= x <= 1<br /> ;; By Lee Mac <br /> (defun asin (x)<br />   (cond<br />     ( (< 1.0 (abs x)) nil)<br />     ( (equal (abs x) 1.0 1e-8) (* x pi 0.5))<br />     ( (atan x (sqrt (- 1.0 (* x x)))))<br />   )<br /> )<br />