Answer:
BC = 18
Explanation:
Since ∠B = ∠C then the triangle is isosceles and so
∠B = ∠C = 45°
Using the sine ratio in the right triangle and
sin45° =
, then
sin45° =
=
=

Multiply both sides by BC
BC × sin45° = 9
, that is
BC ×
= 9
Multiply both sides by

BC = 9
×
= 9 × 2 = 18