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- Tue Mar 31, 2020 5:51 pm
- Forum: Assembly
- Topic: Reimplementing constraint solver
- Replies:
**255** - Views:
**11990**

- Tue Mar 31, 2020 4:08 pm
- Forum: Assembly
- Topic: Reimplementing constraint solver
- Replies:
**255** - Views:
**11990**

- Tue Mar 31, 2020 4:05 pm
- Forum: Assembly
- Topic: Reimplementing constraint solver
- Replies:
**255** - Views:
**11990**

### Re: Reimplementing constraint solver

No, I didn't. Is there a version for an arc, not full ellipse?abdullah wrote: ↑Tue Mar 31, 2020 3:01 pmSurely you know about the specific infinite series for the ellipse.

Something like "Infinite Series 2" of:

https://www.mathsisfun.com/geometry/ell ... meter.html

Then you do not have to subdivide...

- Sat Mar 28, 2020 10:58 pm
- Forum: Assembly
- Topic: Reimplementing constraint solver
- Replies:
**255** - Views:
**11990**

### Re: Reimplementing constraint solver

No, things are worse than that. I changed

And in this case, the accuracy is improving extremely slowly as the number of subdivisions is increased, which is depressing. Something's wrong with my estimate.

*a*to 0.1, and now it takes 32 subdivisions to arrive at error better than 1e-6And in this case, the accuracy is improving extremely slowly as the number of subdivisions is increased, which is depressing. Something's wrong with my estimate.

- Sat Mar 28, 2020 10:53 pm
- Forum: Assembly
- Topic: Reimplementing constraint solver
- Replies:
**255** - Views:
**11990**

### Re: Reimplementing constraint solver

tried. def integrate_ellipse(n): import math from math import sin, cos, sqrt x1 = 0; x2 = math.tau/4 x_samples = [x1 + i/n*(x2-x1) for i in range(n+1)] a = 0.5; b = 1 y_samples = [sqrt((a*cos(x))**2 + (b*sin(x))**2) for x in x_samples] import scipy.integrate return scipy.integrate.simps(y_samples, x...

- Sat Mar 28, 2020 10:51 pm
- Forum: Assembly
- Topic: Reimplementing constraint solver
- Replies:
**255** - Views:
**11990**

### Re: Reimplementing constraint solver

okay, so from my estimate above, I arrived at that to achieve a tolerance of 1e-6*b, I should sibdivide a quadrant of the ellipse into 22 segments for integration. Ok... I probably should give it a try, to see if the value of the integral changes with subdivision by more or less than expected.

- Sat Mar 28, 2020 10:23 pm
- Forum: Assembly
- Topic: Reimplementing constraint solver
- Replies:
**255** - Views:
**11990**

### Re: Reimplementing constraint solver

Actually, that is quite useful. It took me a while, but I estimated that the value will not exceed 40*b in magnitude, probably somewhat less that that in fact, as I mostly assumed that sin^2 and cos^2 are +1, and I flipped quite a few minuses with pluses along the way.

- Sat Mar 28, 2020 9:49 pm
- Forum: Assembly
- Topic: Reimplementing constraint solver
- Replies:
**255** - Views:
**11990**

### Re: Reimplementing constraint solver

Thanks, but it's not very useful. I need some clue on what maximum or average of this thing gets to. I actually would prefer an approximation rather than an exact value, something like "4th derivative is about a*100 in magnitude". Any ideas?

- Sat Mar 28, 2020 4:13 pm
- Forum: Assembly
- Topic: Reimplementing constraint solver
- Replies:
**255** - Views:
**11990**

### Re: Reimplementing constraint solver

@abdullah

I know you can use sage. Can you please figure out average value of fourth derivative of sqrt(sq(a*cos(u)) + sq(b*sin(u))) across the period? I'm trying to find out, how many slices should I take for length integration for arc ellipse to achieve a cretain precision, using Simpson's rule.

I know you can use sage. Can you please figure out average value of fourth derivative of sqrt(sq(a*cos(u)) + sq(b*sin(u))) across the period? I'm trying to find out, how many slices should I take for length integration for arc ellipse to achieve a cretain precision, using Simpson's rule.

- Sat Mar 28, 2020 3:41 pm
- Forum: Help on using FreeCAD
- Topic: [ Solved ] silly problem using partdesign workbench and sketcher
- Replies:
**8** - Views:
**227**

### Re: silly problem using partdesign workbench and sketcher

I would guess you don't know that in openinventor navi style, you have to Ctrl+click to draw and move stuff...