Suppose I draw a Line:
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If I want to draw a line parallel to this line at a distance of 20mm to its left, how do I do it? Use: Line -> Line parallel to given line and at given offset. Select side by clicking to the left of the line. In the offset box, specify offset as 20. And you get a parallel line.
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Perpendicular Line:
Similarly, if I want to draw a perpendicular to a given line how do I do it?
Select: Line ->
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Select the line to which you want to draw perpendicular and the point from which you want perpendicular.
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Line Tangent to two circles:
Suppose I have two circles on my screen:
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If I want to draw a line tangent to both these circles, I select: Line->Line Tangent To Two Circles/Arcs.
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After that I select the two circles. Then a line is
drawn in Green tangent to both the circles.
And a dialog box pops-up in the bottom-right
corner of the Drawing Screen, saying "Is it OK?"
and two buttons: Yes, No.
This means that there are more than one possible lines which are tangent to two circles.
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If I click No, then another possible line is
drawn in Green which is tangent to both the
circles. Again the dialog box is shown asking for
whether this is the Line you wanted or show
you the next possible line.
Now if I click Yes, this line is made final and now
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the Dialog Box disappears. The circles become
Green again. This indicates end of the operation.
I have just drawn all the possible lines (4 lines in all) which are tangent to the two circles:
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