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# drawing arcs

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Hi, does anyone know, how to draw an arc, when having only the starting point, the center and the endpoint? Thanks.

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you may use the formula y=k*x*x , and force the equation
to be solved by trhee points, then iteratively choose the leftmost partion until you reach a fixed value that stands for the granularity of the same curve, then recurse the rightmost part , remember to put a wedge in the recursion formula, that''s to say the fixed value that stops the recursion code.

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If I understand the problem, are we dealing with three points in
space ? if so then why not take a vector from the start point to
the centre point (p) and a vector from the end point to the centre (q) create a tangent at the start point orthogonal to
p ( ie. the dot product is 0 ) and similarly create a tangent
at the end point, and then use a Hermite spline to connect the
two points ( a reasonable textbook will give Hermite''s ). It is
possible to calculate a Hermite iteratively, by 9 additions per point. This solution will allow you to use the end point to
connect to another point in the same way smoothly.

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Isn''t there a less advanced method? Or maybe you could tell me a site, where I could find info on this subject.

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are the 3 points in 2d space?
if so... why not match a circle to them... and draw a sector... ie:

(x-a)^2+(y-b)^2=r^2.

you must solve this for a,b,r (the x,y centre, and the radius).
ie

(x0-a)^2+(y0-b)^2=r^2;
(x1-a)^2+(y1-b)^2=r^2;
(x2-a)^2+(y2-b)^2=r^2;

expand all 3 and solve simulataneously (or look it up)...
then draw a sector of a circle.

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Rutin
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JoeJ
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