float32full.atan help?

Javalin · 2008-08-07 18:36

Hello all,

I am trying to use the floatlib library (float32full bits) to perform atans.

I don't get the answer back I expect compared with my calculator... Help?

This is what I am doing:

OBJ
    float32           : "Float32full"
    floatstring       : "floatstring"

 
pub start
    float32.start
 
    ' 5cm/3.9cm = 1.2820 = 52.04 degree's...!
    
    answer1 := float32.fdiv(5.0,3.9)
    answer2 := float32.atan(answer1)
 
    debug.str(string("a1 ="))    

    debug.str(floatstring.FloatToString(answer1))
    debug.putc(13)
    debug.str(string("a2 ="))    
    debug.str(floatstring.FloatToString(answer2))
    debug.putc(13)
    debug.putc(13)

As return values I get
a1 = 1.282051 (correct)
a2 = 0.9083684 (I am expecting 52.04... degree's)

(note := I have seen the post regarding the atan table error - and have the latest code form obex.parallax.com I believe..!)

Cheers!

James

Mike Green · 2008-08-07 18:46

Usually trig functions deal with angles in radians, not degrees. 2 Pi radians = 360 degrees

Try multiplying by 180 / Pi

Javalin · 2008-08-07 19:02

ah - thanks Mike.

Suspected it might be my maths!
For those interested - the fix is:

CON
    rad2deg       = 57.29577
 
 
PUB Start
    float32.start
    ' 5/3.9 = 1.2820 = 52.04 degree's...!
    
    answer1 := float32.fdiv(5.0,3.9)
    answer2 := float32.atan(answer1)

    answer3 := float32.fmul(answer2,rad2deg)               ' <-------------
 
    debug.str(string("a1 = "))    
    debug.str(floatstring.FloatToString(answer1))
    debug.putc(13)
    debug.str(string("a2 = "))    
    debug.str(floatstring.FloatToString(answer2))
    debug.putc(13)    
    debug.str(string("a3 = "))    
    debug.str(floatstring.FloatToString(answer3))    
    debug.putc(13)
    debug.putc(13)

results are now:
a1 = 1.282051
a2 = 0.9083684
a3 = 52.04567

Cheers

James

Post Edited (Javalin) : 8/7/2008 7:09:23 PM GMT

float32full.atan help?

Comments