VTMO 2026 - Grade 9 - Semifinal - SET 2 - Self-study Question 14

Question 14

Points A,B,C,D lie in this order on a circle of radius 1. Given $AB\parallel CD$, $AB=\frac12CD$ and $AC\perp BD$, find the area of ABCD.

Question illustration

$\frac{9\sqrt2}{5}$
$\frac92$
$\frac95$
$\frac{9\sqrt2}{2}$
$\frac{9\sqrt5}{2}$