From:	Chris Hut <chut AT wesleyan DOT edu>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Trig Help
Date:	Thu, 18 Mar 1999 07:55:53 GMT
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References:	<36EE71C9 DOT 6A160A75 AT bellsouth DOT net>
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  ringo1 AT bellsouth DOT net wrote:
> Hi, IM trying to plot readings gathered from a scanning sonar device. I
> get angle and range readings and would like to see them graphically. But
> my problem is I'm trying to convert the (R,A) into (X,Y) but get
> negative numbers alot of the time. RIght now I'm using an angle of 45
> and varying the range and looking at the data. To get X im using
> R*cos(a), and y = r*sin(a). Its been a long time since trig, but I
> thought this was correct, Can someone tell me whats wrong, my code id
> below.

Your problem (I think...) is that C uses angles measured in radians.  You'll
need to convert your angle measurements into radians and then manipulate
those numbers.	There are 2*pi radians in a circle, so you need to multiply
by your number by 2(pi)/360 or pi/180 to get a new angle which you operate
on.  I think PI is a constant in math.h.  You also need to convert the 10
degrees (in the posangle and negangle initializations) into radians -- that
last detail stumped me when I was trying to figure this out.

> Ringo

Chris

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