angles formed by Secant chords and tangens rules

Chord

a straight line segment whose endpoints both lie on a curve, most commonly a circle

Tangent

a straight line that "just touches" a curve or surface at a single point without crossing through it at that location

Secant

a straight line that intersects a curve at two or more points

When the vertex is on the Tangent-Chord Angle

The angle formed by a tangent and a chord at the point of tangency equals half the measure of the intercepted arc.

Formula for When the vertex is on the angle

Formula: Angle=1/2 x arc

Inscribed Angle

Two Chords

Tangent - Secant

the angle formed is half the difference of the intercepted arcs.

Formula for when the vertex is outside the circle

Angle = ½ x (Far Arc - Near Arc)