OpenEuphoria

Re: trig

• Posted by rudy toews <rltoews at ilos.net> Apr 19, 2004
• 599 views

looking further into my old textbook. or search for "polar coordinates"
did read your second post.

right now you are wanting to compare apples and oranges.
you have to convert to the same means of measurement.
i would pick angles, myself.

equations i sent to you were for a 3d calculation. sphere to radians.
for a 2 d conversion of rectangular co-ordinates to Polar co-ordinates:
x = r cos A,               
y = r sin A
r = sqrroot(x^2 = y^2) ,   
A = arctan(y/x)
sin A = y / (sqrroot(x^2+y^2)),
cos A = x / sqrroot(x^2+y^2)

converting to angles requires only the 4th equation. use positive values!
as you already know x,y of the point to be determined.
looking at only the first 4 entrys in your table of angles, you can now compare
apples to apples and determine which of the first 4 sectors your point falls in.
to determine which of the 4 quadrants requires looking at the sign. a table of
the 4 quadrants:
((1,1),(1,-1),(-1,-1),(-1,1))
with the equations you determine the part of the quadrant, with the sign you
determine which quadrant. remember to rotate 90deg.
ie: 1st sector is equal to the 5th,9th,and 13th sectors, except for the sign.
without pictures, and not being a math teacher , i can not do much else.
once the angle is determined you can use a table of angles to do a lookup of the
angle to find the quadrant number.


rudy
lotterywars