# Find angle for a line of known length to touch another line

Hello and good day. I hope you are all well. I have reached an impasse in translating drafting instructions from paper into seamly2d. You see, I am following along in a book where I am to take a line of a specified measurement and draw it at a certain angle so that the line of specified measurement touches another line while still being that specific measurement. My question is how would I go about doing so? Any help would be greatly appreciated! Thank you for your time.

-Boo

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you can use the tool â€śpoint at intersection of arc and lineâ€ť which can be found on the â€śPointâ€ť menu at the left side of the screen in the Seamly Program. This screenshot shows a red arrow pointing at the icon

That tool will allow you to find the point at which an arc will intersect a line. Study this example. This screenshot shows the history of the operations

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For the purpose of the example, the lengths of lines were arbitrary. I created point B at a 270 degree angle from the origin (point A) using the â€śpoint at distance and angleâ€ť tool. I created point C using the â€śpoint along perpendicularâ€ť tool. Line A_C is perpendicular to line A_B. I created line C_x1 using this tool as a perpendicular to line C_A.

It was not clear to me from the directions you posted whether you knew the slope of the line B_G. I assumed that you did not. I assume that when you use the tool, you will already have Points A, B, C, D, E, and F. I suggest that you create a line C_x1, where x1 is at an arbitrary distance from C. I suggest that you could use 0.25*Line_A_B to place point x1. That would be the length of line A_B divided by 4, and would make the pattern resizable for different sets of individual measurements. I suggest that you create point G by using the tool to find the point at which line C_x1 is intersected by the arc with Point B at the center and radius of 17 3/16 (which is 17.1875)

Good luck and feel free to ask for more help if this does not work as planned. @Grace actually has more experience using the tool for patternmaking than I. She and I have just been looking at a different thread here on the forum. I believe the tool will work for you, but there is a known problem with the tool under certain conditions. So, please speak up if it does not work.

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simple-arc-intersect.val (1.2 KB) here is the pattern file that contains the example I just described for you

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Of course, the one tool I didnâ€™t try!! Ugh, oh my gosh you are a true life saver! Thank you so much for your time and effort, it means so much to me!

-Boo

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Hi Kmf! Thank you for the explanation! I stumbled upon the exact problem. I work with the same pattern system. However, 17 1/8 is the length of BG. We only know the length of BG and the fact that it needs to intersect C x1. How would you proceed in that case? Thank you!

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