Tangency Check

[scottkelley80]

I am in AutoCAD 2008. Is there a quick way to check whether or not a line is tangent to an arc?

 

Thanks!

[ReMark]

Wouldn't the tangent line be at a right angle to the radius of the arc? Any other condition would make the line a secant as it would contact the arc in two places and not one.

[scottkelley80]

yes, that is the definition of a tangent, but how do i verify that someone, other than myself, has drawn a line that is tangent to an arc (i.e. 90 degrees to the radius of the arc). I'm trying to join an arc and a line at their point of tangency (with a tolerance of 0.00) and they won't join, so this leads me to believe that the are not tangent, but I need to be able to verify that they are not.

[eldon]

Try drawing a line from the centre of the circle of the arc, perpendicular to the supposed tangent. Then list the length of this line. If it is the same as the radius of the arc, then the line is a tangent. You may have to increase the number of decimal places displayed to ensure that they are equal.

[scottkelley80]

It looks like they are both the same length/radius. Any other ideas on why I can't get the lines to join?

[eldon]

Sometimes you have to encourage AutoCAD. Click on the line, then grab the end with a hot grip and move it to the endpoint of the arc.

[Guest dingo]

try copy/rotate. draw a line from the centre of the arc/circle to a predetermined point on the arc. then copy/rotate that line, using the arc end of the line as the reference point, rotation angle 90 or -90 degs, as required.

 

Bob's your uncle.