The chord-chord angle is an angle formed by two chords that intersect in the interior of a circle.
If chords 
and 
intersect at 
, the measure 
of 
satisfies
![theta=1/2[arcAC+arcBD],](/images/equations/Chord-ChordAngle/NumberedEquation1.svg) |
where the two arcs are those intercepted by the angle and its vertical angle. Thus an angle formed by two intersecting chords equals half the sum of the measures of the intercepted arcs.
