So ∠C=∠E ∠BAC=∠DAE.
Because ∠BAC=∠BAD+∠DAC ∠DAE=∠DAC+∠CAE.
So ∠BAD=∠CAE
Because ∠C=∠E ∠DFC=∠AFE
So ∠CDE=∠CAE
So ∠CDE =∠ bud ∠ABD=∠ADB=∠ADE.
(∠ABD=∠ADB because △ABD is an isosceles triangle)
Because ∠ Abd+∠ ADB+∠ Bad = 180, ∠ ADB+∠ Ade+CDE = 180.
So: ∠ CDE =180-∠ ADB-∠ ade =180-∠ Abd-∠ ADB = ∠ bad.