Point/On,A,Atangl
Point on Arc at Angle
Creates a point on an existing arc at a specified angular position.
What It Does
The Point/On,A,Atangl operator creates a point on the circumference of an arc at a specified angular position. The angle must fall within the arc sweep — between the start and end angles of the arc.
Arc sweep check: The specified angle must be within the arc sweep. If the angle falls outside the arc, XyzPilot returns an error.
Syntax
Point/On, A, Atangl, Angle, Z
Quick Input
A: [arc reference]
Angle: [angle in degrees — must be within arc sweep]
Z: 0
Direction Selector
No direction selector is required. The result is uniquely determined by the input geometry.
Worked Examples
Setup:
A0 = Arc: centre (0,0), r=50, start=0°, end=90° CCW
Point/On, A0, Atangl, 45, 0
→ P0 = (35.355, 35.355) [at 45° — within sweep ✓]
Point/On, A0, Atangl, 90, 0
→ P1 = (0, 50) [at 90° — arc end point ✓]
Point/On, A0, Atangl, 120, 0
→ Error: 120° is outside the arc sweep (0° to 90°)
Analytic Rule
Point on arc at angle A:
x = cx + r * cos(A)
y = cy + r * sin(A)
Angle must satisfy: start_angle ≤ A ≤ end_angle (CCW)
or: end_angle ≤ A ≤ start_angle (CW)
Result: Exact analytic coordinates.
FAQ
What if the angle is outside the arc sweep?
XyzPilot returns an error. The angle must fall within the arc sweep angles. Use Point/On,C,Atangl for full circles where any angle is valid.
How do I find the arc start and end angles?
Use the Geometry Information Display or Show Coordinates panel to view the arc properties including start_angle, end_angle, and sweep_degrees.