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February 21st, 2009, 02:00 PM  #1 
Newbie Joined: Feb 2009 Posts: 2 Thanks: 0  Solve angle and radius of oval
I have a formula: X = (radius*n+f)*sin(a) Y = radius*cos(a) Which, when plotted, gives me a very flat oval when the radius is small moving out to a circle and then to a tall oval. (eg. n = 0.55, f=195, becomes a circle when the radius is approx 433.333) Now what I need is to be able to reverse the formula. I have the values for X, Y, n, f. I need to calculate rad and a. If I rearrange the formula to : X = ((Y/cos(a))*n+f)*sin(a) or X = Y*n*sin(a)/cos(a) + f*sin(a) All values are known except a. But how do I rewrite this so I have a formula a = ......... 
February 21st, 2009, 04:55 PM  #2 
Global Moderator Joined: Dec 2006 Posts: 20,978 Thanks: 2229 
You can use sin²a + cos²a = 1 to eliminate a, and then solve the resulting quartic equation for the radius.


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angle, oval, radius, solve 
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