gongfuenglish
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共回答了14个问题采纳率:100% 举报
S△AEH = 1/2×AE×AH
= 1/2×(1/2×AB)×AH
= 1/4×AB×AH
S△EBF = 1/2×BE×BF
= 1/2×(1/2×AB)×(1/2×BC)
= 1/8×AB×BC
= 1/8×36
= 9/2
S△HFC = 1/2×FC×AB
= 1/2×(1/2×BC)×AB
= 1/4×AB×BC
= 1/4×36
= 9
S△HCG = 1/2×CG×DH
= 1/2×(1/2×AB)×DH
=1/4×AB×DH
S阴影 = S矩形 - (S△AEH + S△EBF + S△HFC + S△HCG )
= 36 - (1/4×AB×AH + 9/2 + 9 + 1/4×AB×DH)
= 36 - [27/2 + 1/4×AB×(AH+DH)]
= 36 - (27/2 + 1/4×AB×BC)
= 36 - (27/2+1/4×36)
= 36 - 45/2
= 27/2
1年前
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