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  1. mike0709lum

    Maths Problem - Partial Ellipse 1st Moment of Area

    IDS, Had a bit of a play with your integration xcel file, really useful, I'm sure others will find it useful also. Thanks for sharing that. Cheers, Mike
  2. mike0709lum

    Maths Problem - Partial Ellipse 1st Moment of Area

    Thanks Zekeman (& ione), Worked a treat. I hadn't realised that centering the ellipse would work but thinking about the area and centroid relationships I see that it makes sense. Useful fact to bear in mind and simplifies the problem greatly. Cheers, Mike
  3. mike0709lum

    Maths Problem - Partial Ellipse 1st Moment of Area

    Thanks ione, Haven't you missed b^2 from y = ? I get: y=sqrt[b^2-b^2(x-c)^2/a^2] assuming I'm right dy is then: dy=-[b^2(x-c)/[a*sqrt(b^2-b^2(x-c)^2/a^2)]]dx IRstuff - it's part of a design optimisation so need to keep the symbols for the design process. If I just needed one value I'd...
  4. mike0709lum

    Maths Problem - Partial Ellipse 1st Moment of Area

    Thanks rb1957, You're right, I need to double the result to account for the -ve of y, I'd overlooked that. Unfortunately the error is not fully accounted by this. In fact I'm having difficulty in getting a workable integration. Since writing the original post I found an error in my excel...
  5. mike0709lum

    Maths Problem - Partial Ellipse 1st Moment of Area

    Thanks for the reply but the issue I have is I am performing the calculation to determine the centre of mass of the section where x>0. Also, since it is just part of the ellipse the area is not PI*a*b but I've got that equation nailed. Mike
  6. mike0709lum

    Maths Problem - Partial Ellipse 1st Moment of Area

    Hi, Looking for some help on a maths problem, I'm a bit rusty and can't see what I'm doing wrong. I'm trying to calculate the first moment of area of a portion of an ellipse which is not centered at 0,0. The ellipse is described by: (x-c)^2/a^2 + y^2/b^2 = 1 , this means the centre is at...

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