Arc/Line,A1
Line Tangent to Arc at Endpoint
Creates a line tangent to arc A1 at its start or end point. The tangent direction is perpendicular to the radius at the selected endpoint.
What It Does
The Arc/Line,A1 operator creates a line tangent to an arc at either its start or end point. The tangent direction is always exactly perpendicular to the radius at the selected endpoint.
This operator is equivalent to
Line/Tanto,A — both create a line tangent to an arc at its endpoint. The syntax differs but the result is identical.Syntax
Arc/Line, A1, Start|End
Quick Input
P: 0
A: 0
Arc End: Start End
Direction Selector
| Selector | Result |
|---|---|
Start | Tangent line at the arc start point |
End | Tangent line at the arc end point |
Worked Examples
Setup:
A0 = Arc: centre(0,0), r=50, start=0, end=90 CCW
Start point: (50,0) at 0 degrees
End point: (0,50) at 90 degrees
Arc/Line, A0, Start
→ L0: through (50,0), direction=90 degrees (vertical)
Radius at 0 degrees points right (+X)
Tangent is perpendicular = vertical
Arc/Line, A0, End
→ L1: through (0,50), direction=0 degrees (horizontal)
Radius at 90 degrees points up (+Y)
Tangent is perpendicular = horizontal
Analytic Rule
Tangent direction at arc endpoint:
Radius direction at angle A: (cos A, sin A)
Tangent direction: perpendicular = (-sin A, cos A)
For Start: A = start_angle
For End: A = end_angle
Tangent line passes through the endpoint
in the tangent direction.
Result: Exact analytic tangent line.
FAQ
Is this the same as Line/Tanto,A?
Yes. Arc/Line,A1 and Line/Tanto,A produce identical results. The syntax differs — use whichever matches your workflow.
Why is the tangent perpendicular to the radius?
By definition, a tangent to a circle at a point is perpendicular to the radius at that point. This is a fundamental property of circles and arcs.