解：$∠DEC=∠DCE $
∵五边形的内角和是$(5-2)×180°= 540°，$且每个内角都相等
∴每个内角的度数为$540°÷5= 108°$
即$∠A = ∠AED = ∠D = 108°$
$∵AB∥EC$
$∴∠A+∠AEC=180°$
$∴∠AEC =180°-∠A =72°$
$∴∠DEC= ∠AED-∠AEC =36°$
$∵△DEC $的内角和为$180°$
$∴∠DCE=180°-∠DEC-∠D=36°$
$∴∠DEC=∠DCE$
