如图是一个等腰梯形状的水渠的横切面图,已知渠道底宽BC=2米,渠底与渠腰的夹角∠BCD=120°,渠腰CD=5米,求水渠的上口AD的长.
如图是一个等腰梯形状的水渠的横切面图,已知渠道底宽BC=2米,渠底与渠腰的夹角∠BCD=120°,渠腰CD=5米,求水渠的上口AD的长.
其他人气:793 ℃时间:2020-06-07 14:36:09
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过C和B分别作CE⊥AD,BF⊥AD(1分)∵∠BCD=120°∴∠ECD=30°(2分)∴ED=12CD=12×5=2.5(4分)∴四边形ABCD为等腰梯形,∴AB=CDBF=CE∴△AFB≌△DEC,∴AF=ED=2.5(5分)∵EF=BC=2∴AD=DE+EF+FA=2.5+2+2.5=7(...
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