Create new point with two known lengths

[artlass]

Hello all. I wish to triangulate a point using two known lengths- but no known angles- and the triangulation is not a right angled triangle!

Basically it is to create a fitted jacket shoulder dart using the Aldrich method, using ( I must admit) an older version of Valentina. I need to create point A22 , or more precisely the line A25- A22- which I have drawn in here “manually”. My first dart line is A21-A25. A22 - A25 is of equal length to A21-A25 and needs to be a specified length (#dart) from A21.

Here on my screen shot I have fudged A22 manually, creating an arc and then a line of fixed length, they I eyeballed into approximately the right position. This is no good to me in for the future obviously, because I need the lengths to be linked parametrically to the the other measurements.

I thought I could use the intersect arc tool- but it does not allow me to define the length- only the angle.

I feel like I am missing something really obvious, but in the forums have not found this precise question… I would be most grateful for any pointers. Thankyou, Anna

[Grace]

Hello, @artlass , and welcome to the Seamly forum.

All you need to do is to draw another arc from A25 that intersects the arc from A21, at the distance of the line A25 to A21. Then you need to use the tool to place a point at the intersection of the 2 arcs.

I’m on the latest version of Seamly2D, so I’m not too sure where the tool is in an older version of Seamly or Valentina, so I hope this helps you.

[artlass]

Oh of course! Thankyou so much. Can I just say I have read so many of your replies as I muddle my way through this forum, trying to figure things out- and I think you are a bit of a super hero. Your time and care in answering is sincerely appreciated!

[Grace]

Thank you very much, @artlass , but we’re a dedicated team. If 1 doesn’t answer, another will.