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How To Plot A Curve With Given Three Points? 
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#1
Aug811, 10:08 PM

P: 80

Hi everyone,
Can someone please tell me is there any mathematical equation/formula on ploting a curve with given three coordinates/points such as below image? Thank you very much for your help Op 


#2
Aug811, 10:42 PM

HW Helper
P: 925

There are infinitely many curves you can draw through three points. The simplest method it to use a 2nd order polynomial (i.e a parabola). Just write out 3 equations using the values of x & y:
y_{1} = a x^{2}_{1} + b x_{1}+ c y_{2} = a x^{2}_{2} + b x_{2}+ c y_{3} = a x^{2}_{3} + b x_{3}+ c This is 3 equations in 3 unknowns (a,b,c) that can be solved by substitution. 


#3
Aug811, 11:29 PM

Sci Advisor
P: 2,751

As hotvette has already said, there are infinitely many curves you can draw through three points.
Two common cases in which the curve is uniquely specified by three points are the parabola and the circle. That is, if you assume it's a circle then such a circle is unique, and if you assume it's a parabola then such a parabola is unique. 


#4
Aug911, 12:52 AM

P: 756

How To Plot A Curve With Given Three Points?



#5
Aug911, 08:24 PM

P: 80

Will above equations can be continued from three to nine equations with similar pattern? Does this curve is a kind of smooth and continue curve? 


#6
Aug1011, 01:59 AM

Sci Advisor
P: 2,751




#7
Aug1011, 07:25 AM

P: 460

If all 3 point's are colinear then it can't be a circle or a parabola, unless the radius of the circle goes to infinity or the coefficient of x^2 goes to infinity or zero for the parabola. It can be many other things but the best representation is probably a straight line, unless you have some kind of 'exotic' application such as temperature changes over time.



#8
Aug1011, 08:42 AM

P: 1,212

For nine points I think you'll need a 9th order polynomial, so you'd get nine equations (and a headache). Something tells me the reasoning stems from the fundamental theorem of algebra, but I couldn't give you more detail than that.



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