第1个回答 2014-06-01
∵ABCD是平行四边形,∴AB∥CD,∴∠A+∠D=180°,
∵AE=AF,∴∠AEF=1/2(180°-∠A)=1/2∠D,,
∵∠CEF=90°,
∴∠DEC=180°-(∠AEF+∠CEF)=90°-1/2∠D,
∴∠DCE=180°-(∠D+90°-1/2D)=90°-1/2∠D,
∴∠GEC=∠DEC,
∴DE=DC,
∵AE:DE=3:8,
设AE=3K,则DE=CD=AB=5K,
∴S1=2/5×1/2×40=8,
S2=3/5×3/8×40=9,
∴S1+S2=17。本回答被网友采纳