Rectangle $ABCD$ contains a point $X$ such that $AX = 3$, $BX = 3$, and $CX = 3$. Find $DX$.
British Flag Theorem
AX^2 +CX^2 =BX^2 + DX^2
3^2 + 3^2 = 3^2 + DX^2
18 = 3^2 + DX^2
18 - 9 = DX^2
DX^2 =9
DX = 3
+412 
