题目内容
如图所示,若∠1=∠2,则________∥________;若∠3=∠4,则________∥________;若∠5=∠6,则________∥________;若∠7=∠8,则________∥________;若∠BAD+∠ABC=,则________∥________;若∠ABC+∠BCD=,则________∥________
若|x|=,则x=________
在ABCD中,(1)若∠A=,则∠B=________,∠C=________,∠D________.
(2)若∠A-∠B=,则∠A=∠C=________,∠B=∠D=________.
(3)若∠A=2∠B,则∠A=∠________=________,∠B=∠________=________.
(4)若△ABCD的周长为40cm,且BC比AB长2cm,则AB=________=________cm,BC=________=________cm.
(5)若ABCD的周长为32cm,BC=AB,则AB=________cm,BC=________cm.
我国汉代数学家赵爽为了证明勾股定理,创制了一幅“弦图”,后人称其为“赵爽弦图”(如图1).图2由弦图变化得到,它是用八个全等的直角三角形拼接而成,记图中正方形ABCD,正方形EFGH,正方形MNKT的面积分别为S1,S2,S3.若S1+S2+S3=10,则S2的值是( )
如图,在边长为12的正方形ACBE中,D是边AC上一点,若tan么DBA=,则AD的长为 ( ▲ )
A.4 B.2 C.2 D.2