The area of a rectangle is 120 square centimeters. EF is the midpoint of BC and CD respectively. How to calculate the area of the shadow?

The area of a rectangle is 120 square centimeters. EF is the midpoint of BC and CD respectively. How to calculate the area of the shadow?

Let any rectangle ABCD, ab = CD = a, BC = ad = B, S & # 10240; ABCD = 120 square centimeter, e and f be the midpoint of BC and CD respectively
∵ arbitrary rectangle ABCD, ab = CD = a, BC = ad = B, S & # 10240; ABCD = 120 square centimeter,
E. F is the midpoint of BC and CD respectively
∴ DE=EC=AB×1/2=CD×1/2=a×1/2
BF=FC=BC×1/2=AD×1/2=b×1/2
∠ abd = ∠ BCD = ∠ CDA = ∠ DAB = RT ∠ (right angle)
∵ arbitrary rectangle ABCD, S & # 10240; ABCD = 120 square centimeter
S & # 10240; ABCD = ab × BC = CD × ad = 120 square centimeter
A × B = 120 square centimeter
(1) Calculate the area of △ ECF s △ ECF:
S△ECF=FC×EC×(1/2)
=(CD×1/2)×(BC×1/2)×(1/2)
= CD×BC×(1/8 )
=A × B × (1 / 8) and ∵ a × B = 120 square centimeter
S △ ECF = 120 square cm × (1 / 8)
=15 square centimeters
(2) Finding the area of Pentagon abfde s Pentagon abfde
S Pentagon abfde = S & # 10240; ABCD - s △ ECF
=120-15
=105 square centimeters