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# how to calculate the distance between the two point on the ellipse

edited November 2013
``````                       ***********************************************
***                                                 ***
**                                                         **
*                                                               x1
*                                                                   x
*                                                                       x
*                                                                         x
*                                                                         x
*                                                                       x
*                                                                   x
*                                                               x2
**                                                         **
***                                                 ***
***********************************************
``````

if i have the equation of ellipse (x/a^2+y/b^2=1),a,b and x’s coordinates is known now,how to calculate the the length of curve between the two point???

Tagged:

• Why this isn't in the How To category, given the formulation of the subject?... Moved!

Looks more like a math question (assignment, likely) than a programming question... So that's not about Using Processing at all.

Perhaps you can use your Internet connection to Google about formulae giving the length of an arc?

• i found nothing about it and it's true that the problem is about math , but i am an art student , and don't have learn higher mathematics so i hope there's someone on the internet can slove this

• do points 1 and 2 have the same value of x? i assume they so.

i'm not sure i trust that equation you posted in the form you have it.

(x / a) ^ 2 + (y / b) ^ 2 = 1

so, with some rearranging

y = b * sqrt(1 - ((x / a)^2))

so your distance will be twice that...

• `y = b * sqrt(1 - ((x / a)^2))`

I guess that'd be... :-B

``````float y = b*sqrt(1 - sq(x/a));
``````
• sorry the value of x for two points doesn't same , and i want to get the distance between them ,witch is shown with the mark 'x'

• How do you define which points you need? For a given x, you have two points on the ellipse.