1. atan2
i think atan2(x, y)
is sposed to return a, where sin(a) = x and cos(a) = y
anyone know how to do this?
thanx.
2. Re: atan2
Mark Honnor writes:
> i think atan2(x, y)
> is sposed to return a, where sin(a) = x and cos(a) = y
> anyone know how to do this?
Probably it's the other way around:
sin(a) = y and cos(a) = x
and therefore tan(a) = sin(a)/cos(a) = y/x
So a = arctan(y/x) *except* that Euphoria's arctan() function
always returns an angle between -PI/2 and +PI/2, so
to find out the true angle you must *also* take the sign +/- of x
and y into account to see what quadrant you are in.
e.g. if x is negative and y is positive
the angle must be greater than PI/2 and less than PI.
(There are 2PI radians in a circle, i.e. 360 degrees)
If x is positive, arctan() should give you the correct result,
but if x is negative you'll have to compute PI plus or minus the
angle given by arctan(). I'd draw a diagram but it would be
messed up by proportional fonts.
Regards,
Rob Craig
Rapid Deployment Software
http://members.aol.com/FilesEu/
3. Re: atan2
Liquid-Nitrogen Software wrote:
>
> i think atan2(x, y)
> is sposed to return a, where sin(a) = x and cos(a) = y
> anyone know how to do this?
>
> thanx.
------------------------------------------------------------------------------
include misc.e -- PI
--
c2PI = 2*PI,
cPIH = 0.5*PI
------------------------------------------------------------------------------
function arctan2 ( object y, object x) -- returns 4 quadrant angle
[-ã,ã)
sequence s -- x and y have to have equal
structure!
if atom(x) then
if x > 0 then
return arctan(y/x)
elsif x < 0 then
if y > 0 then
return arctan(y/x) + PI
elsif y < 0 then
return arctan(y/x) - PI
else -- y = 0
return -PI
end if
else -- x = 0
if y > 0 then
return cPIH
elsif y < 0 then
return -cPIH
else -- y = 0
return 0
end if
end if
end if
-- sequence s
s = repeat(0,length(y))
for i = 1 to length(y) do
s[i] = arctan2(y[i],x[i])
end for
return s
end function
------------------------------------------------------------------------------
Hope this helps.
Nave a nice day, Rolf
