Angles

Angle marking for geometry diagrams.

API Reference

geolet.primitives.angles.api.Angle

Angle(p1: PointT, p2: PointT, p3: PointT, *, label: str = '', n: int = 1, radius: float = 0.4, color: str = 'black', fill: bool = False, right_angle: bool = False) -> AngleT

Create an angle marking at a vertex between two rays.

Uses standard geometry notation: Angle(A, B, C) marks the angle ABC, which is the angle at vertex B with rays BA and BC.

Uses Asymptote's markangle function from the markers module to draw an arc marking the angle (counterclockwise from first ray to second).

Parameters:

Name	Type	Description	Default
p1	PointT	First point (A in angle ABC).	required
p2	PointT	The vertex of the angle (B in angle ABC, where the arc is drawn).	required
p3	PointT	Third point (C in angle ABC).	required
label	str	Angle label (e.g. "\alpha", "45°"). Empty for no label.	''
n	int	Number of arc marks (1, 2, 3 for congruent angle notation).	1
radius	float	Arc radius in cm.	0.4
color	str	Asymptote color name (e.g. 'black', 'red', 'blue').	'black'
fill	bool	Fill the angle sector with semi-transparent color.	False
right_angle	bool	Draw square marker for 90° angles instead of arc.	False

Returns:

Type	Description
AngleT	An angle marking drawable satisfying AngleT protocol.

Examples

Basic Angle Marking

from geolet import Point, Segment, Angle, autofigure


@autofigure
def angle_example():
    A = Point("A", 3, 2, label_dir="NE")
    B = Point("B", 0, 0, label_dir="SW")
    C = Point("C", 4, 0, label_dir="SE")

    Segment(B, A)
    Segment(B, C)

    # Mark angle ABC at vertex B
    Angle(A, B, C, label=r"$\alpha$")

Right Angle

from geolet import Point, Segment, Angle, autofigure


@autofigure
def right_angle():
    A = Point("A", 0, 2, label_dir="N")
    B = Point("B", 0, 0, label_dir="SW")
    C = Point("C", 3, 0, label_dir="SE")

    Segment(B, A)
    Segment(B, C)

    # Square marker for 90° angle
    Angle(A, B, C, right_angle=True)

Multiple Arc Marks

from geolet import Point, Segment, Angle, autofigure


@autofigure
def congruent_angles():
    A = Point("A", 0, 0, label_dir="SW")
    B = Point("B", 4, 0, label_dir="SE")
    C = Point("C", 2, 3, label_dir="N")

    Segment(A, B)
    Segment(B, C)
    Segment(C, A)

    # Mark congruent angles with same number of arcs
    Angle(B, A, C, n=2, color="blue")
    Angle(A, B, C, n=1, color="red")
    Angle(A, C, B, n=2, color="blue")

Filled Angle

from geolet import Point, Segment, Angle, autofigure


@autofigure
def filled_angle():
    A = Point("A", 2, 2, label_dir="NE")
    B = Point("B", 0, 0, label_dir="SW")
    C = Point("C", 3, 0, label_dir="SE")

    Segment(B, A)
    Segment(B, C)

    Angle(A, B, C, fill=True, color="blue")