Given a line with slope y/x, find a simple formula for the slope of a second line that forms a 45 degree angle with this line (find slopes for both 45 degrees more and 45 degrees less.)
This can be done without trigonometry.
Find a general formula for any angle.
This requires trigonometry.
(In reply to
re: Solution  how do you use it? by Jer)
If you know the slope p/q for the angle (like you know the slope y/x of the line), then use the p and q; otherwise, use q = 1 and p = tan(angle).
For the case of 30 degrees, the slope is 1/sqrt(3). So p = 1 and q = sqrt(3) or q = 1 and p = tan(30) = 1/sqrt(3).
Edited on March 22, 2006, 6:07 pm

Posted by Bractals
on 20060322 17:59:09 