The area of △ AEF is equal to the area of trapezoidal EFBC

The area of △ AEF is equal to the area of trapezoidal EFBC

Because EF / / BC
So △ AEF ∽ ABC
So s △ AEF / s △ ABC = EF ^ 2 / BC ^ 2
Because the area of △ AEF is equal to the area of trapezoidal EFBC
So s △ AEF / s △ ABC = 1 / 2
So EF ^ 2 / BC ^ 2 = 1 / 2,
That is, EF ^ 2 / (2 √ 2) ^ 2 = 1 / 2
The solution is EF = 2