So, ∠EBF=90
And because in the isosceles triangle ABC, ∠A=∠B=45.
Therefore, < ∠CBF=45.
Because, AC = AB and AD = BF.
So triangle CAD is equal to triangle CBF (corner edge)
So ∠ACF=∠BCF, CD=CF because ∠ACD+∠DCB=90.
So ∠BCF+∠DCB=90, which means ∠DCF=90.
Because ∠ DCE = 90
So ∠ECF=45 connects E and F.
Because CD=CF, ∠DCE=∠ECF=45, CE=CE.
So all triangles DCE are equal to triangle ECF (corner edge)
So DE=DF, so in the right triangle EBF? +BF? =EF? So de? =AD? +BE?