distance along a line as one end point to a new line

[EMUGOD]

I am trying to make a new line 7.4 units long, at the proper angle to intercept with the vertical extension of the intercept point of the two circles. It seems like i should be able to type in the length value while the cursor is snapped to the extension to do this, but that doesn't work, instead just taking the current angle and extending as far past the cursor as needed to make the final line 7.4 units long. Is there any way to do this?

 

I have tried zooming in very close and adjusting it manually, which initially seems to work, but causes problems later (a few steps later and pieces built outward some piece will gain a thousandth of a millimeter, a few more additions and one gains a millimeter, etc.).

 

I'm sorry if there is some other term for this and it is a common question, i tried searching but it is a difficult thing to describe and i don't know any technical term for it.

[eldon]

Your diagram is a bit on the small side, but you may have to do a bit of construction if you want to get exactness.

 

Try drawing a circle of radius 7.4, centered on the end of the vertical line. Draw the vertical extension. Then you can draw your line to the actual intersection point.

[EMUGOD]

Your diagram is a bit on the small side

 

Yea, i don't know what happened, the forum automatically resized it to less than a quarter the original size? This one should be better; i'm trying to do the same thing with a line 10 units long.

 

Try drawing a circle of radius 7.4, centered on the end of the vertical line. Draw the vertical extension. Then you can draw your line to the actual intersection point.

 

Centered on the end of which vertical line? The two lines i have coming downward from the center of the circles are of arbitrary length. I was attempting to construct to solve this, i forget exactly how, but whatever it was didn't work, and turned out to be a pretty silly idea.

 

It occurred to me that basically what i am trying to do is construct an equatorial triangle (which will be used for other constructions and eventually discarded, but still). I realise this can be done easily with the polygon command (and some rotating/scaling), but even so how to do the initial problem would be interesting to know.

[eldon]

I would not try and use snaps when drawing a line at a particular angle.

 

One way of drawing angles at 60° is to set up the Polar angle to 30°, and then the line will snap to the angle. It is very difficult, if not impossible to draw accurately on the dynamic information, and far easier to do a bit of construction and erase lines after.

[EMUGOD]

It is very difficult, if not impossible to draw accurately on the dynamic information, and far easier to do a bit of construction and erase lines after.

 

right now i'm more worried i'm falling into the habit of constructing when there is no need to...

[eldon]

I might not have used so many construction lines in those examples, but everyone develops their own way of working, and you may be quicker drawing a few extra lines and cleaning up afterwards.

 

I have recently found that Polar tracking can be very useful, after ignoring it for a long time