<-- a
<-- b
<-- c
<-- d
<-- angle 1 α
<-- angle 2 γ
  

The following practice problem has been generated for you:
Given a quadrilateral with sides a = 15, b = 15, c = 6, and d = 6 with opposite angles α = 53 and γ = 53, calculate the area using Bretschneider's formula