Tangent

[cbutton69]

Is there a way to draw a line tangent to an ellipse? I can do it by visually placing the line, but I'm not sure it is accurately tangent.

[steve.ledger]

Enabling 'snapping' (num *) will allow an object to snap to a line at a perfect tangent

[raynerj1]

My way is a little bit more complex than Steve's...

1. I just draw a guide line, (have snap to guides turned on)
2. snap my elipse to the guide
3. draw my line and also snap it to the guideline.

[ss-kalm]

When you select the object, how can you be sure that your snap location is at a perfect tangent. Aren't you just selecting visually? The snap seems to snap to the nearest point, unless you happened to pick the nearest point exactly, it doesn't seem to me to pick a perfect tangent.

Just being obtuse, deliberately don't pick the approx. tangent point to snap. Xara doesn't find the tangent point, therefore when you snap you are only getting approximate points.

Am I doing something wrong?

[cbutton69]

Keith, that's what I thought.

[cbutton69]

Let's say I have an ellipse and a line segment as shown in the attached XAR file. How do I attach the line to the ellipse as a tangent?

[steve.ledger]

Not sure I understand the problem guys.
With snapping turned on, drag the ellipse to the line at the point you want it to snap (defined by the position of the mouse cursor). Works fine for me. Certainly not a hit'n'miss affair.

Check out the movie folder and run magnet_small.avi

C:\Program Files\Xara\Xara Xtreme Pro 4\HelpAndSupport\ENG

[steve.ledger]

Am I doing something wrong?

Yeh - you're deliberately trying to not pick the right point. Why would you do this

[ss-kalm]

Because you can't arbitrarily pick the "right" point to get a perfect tangent like that. If you want to get a correct tangent there is only one correct point, and you can't pick it by guessing!

If you want a correct tangent you have to have the tangent line at exactly 90° to the radius of the circle.

If you draw the radius, copy it, rotate it by 90° and snap them together, that should give an exact tangent. However, I'm not certain where Xara will snap. Does it pick the end point of the line in preference to a near point?

My point is that the original post asked for a accurate tangent, not an approximate tangent. An approximate tangent is easy.

EDIT - Just realised - Can't run the movies since rebuilding my system - will check them out as soon as I can fix it.

[steve.ledger]

I guess it depends on what you define as a tangent.
Googling gives several interpretations.
I've always understood it to be a straight line touching a curve at a single point without crossing it.