# Math Help - Quadrilateral ABCD

Quadrilateral $ABCD$ is inscribed in a circle, where the tangents to this circle at points $B$ and $D$ intersect on the straight line joining $A$ and $C$. Show that:

$AB\cdot{CD}=AD\cdot{BC}$

Quadrilateral $ABCD$ is inscribed in a circle, where the tangents to this circle at points $B$ and $D$ intersect on the straight line joining $A$ and $C$. Show that:
$AB\cdot{CD}=AD\cdot{BC}$