Secant

• If two secants intersect in the exterior of a circle

  Secant-secant product theorem
• If two chords intersects in the interior of a circle

  Chords- chords product theorem
• If a line is tangent to a circle, then it is perpendicular.

  Theorem 1
• If a tangent and a secant(or chord) intersect on a circle at the point of tangency.

  Theorem 9
• If two secants or chords intersects in the interior of a circle.

  Theorem 10