【简答题】已知O为△ABC的外心,以线段OA、OB为邻边作平行四边形,第四个顶点为D,再以OC、OD为邻边作平行四边形,它的第四个顶点为H. (1)若 OA = a , OB = b , OC = c , OH = h ,试用 a 、 b 、 c 表示 h ; (2)证明: AH ⊥ BC ; (3)若△ABC的∠A=60°,∠B=45°,外接圆的半径为R,用R表示 | h | .
【简答题】已知ABCD为平行四边形,A(﹣1,2),B (0,0),C(1,7),则D点坐标为( ).
【简答题】II . 单句语法填空 1. It is no use _________ (reason) with him. 2 . You'd better get your hair ___ (cut) . 3 . Many countries participated __ the war which broke out in Libya. 4 . When I came in, he was fill...
【单选题】在TCP/IP体系结构中,UDP协议工作在()
【判断题】You'd better use good bags while travelling.
【单选题】已知命题 平行四边形的对角线互相平分,命题 平行四边形的对角线相等,则下列命题中为 真命题的是( )
【单选题】六个面都是平行四边形的四棱柱称为平行六面体.已知在平行四边形ABCD中,AC 2 +BD 2 =2(AB 2 +AD 2 ),则在平行六面体 ABCD-A 1 B 1 C 1 D 1 中,AC 1 2 +BD 1 2 +CA 1 2 +DB 1 2 等于( )
A.
2(AB 2 +AD 2 +AA 1 2 )
B.
3(AB 2 +AD 2 +AA 1 2 )
C.
4(AB 2 +AD 2 +AA 1 2 )
【简答题】填空 dress, throughout, offer, make up, advise 1. You'd better_______ in layers because it is very cold outside. 2. The old man__________ the children to read more books and get more knowledge. 3. There...
【单选题】在TCP/IP体系结构中,UDP协议工作在( )