梯形ABCD中,AD//BC,AD=1,BC=4 ∠C=70 ∠B=40 ,则AB的长为 A1 B2 c3
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![梯形ABCD中,AD//BC,AD=1,BC=4 ∠C=70 ∠B=40 ,则AB的长为 A1 B2 c3](/uploads/image/z/15109936-16-6.jpg?t=%26%23160%3B+%E6%A2%AF%E5%BD%A2ABCD%E4%B8%AD%2CAD%2F%2FBC%2CAD%3D1%2CBC%3D4+%E2%88%A0C%3D70+%E2%88%A0B%3D40+%2C%E5%88%99AB%E7%9A%84%E9%95%BF%E4%B8%BA%26%23160%3BA1%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3BB2%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B+c3%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B%26%23160%3B)
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梯形ABCD中,AD//BC,AD=1,BC=4 ∠C=70 ∠B=40 ,则AB的长为 A1 B2 c3
梯形ABCD中,AD//BC,AD=1,BC=4 ∠C=70 ∠B=40 ,则AB的长为
A1 B2 c3 D4
梯形ABCD中,AD//BC,AD=1,BC=4 ∠C=70 ∠B=40 ,则AB的长为 A1 B2 c3
用计算器得tan70=2.74
tan40=0.84
设高为x
底边4=x/tan70+x/tan40
x=2.57
y=2.57/tan40=3
AB^=2.57^+3^
AB=3.95
选D