如圖，矩形ABCD中，BE平分∠ABC交AD于E，AB=2，CE=4，則∠BEC=________°．

矩形ABCD中，AB=3，BC=4，BE⊥AC于E，則BE=________．(用小數(shù)表示)

矩形的周長(zhǎng)為24cm，一邊中點(diǎn)與對(duì)邊兩頂點(diǎn)的連線成直角，則矩形兩鄰邊的長(zhǎng)分別為_(kāi)______   ,________．(先填小的邊)

矩形ABCD對(duì)角線AC，BD相交于點(diǎn)O，AB=10，BC=8，則△AOB的周長(zhǎng)是________．

有一個(gè)角是直角的________形是矩形，對(duì)角線________的四邊形是矩形．

矩形的對(duì)邊________，對(duì)角線________，四個(gè)角都是________．

矩形ABCD的對(duì)角線AC、BD交于O點(diǎn)，∠ACB=∠BOC，若AC=10cm，則AD= ________cm．

矩形兩條對(duì)角線夾角為，兩條對(duì)角線的和為8cm，則此矩形較短邊的長(zhǎng)是________cm．

兩條對(duì)角線________的平行四邊形是矩形．

矩形的兩條對(duì)角線的交角之一是60°，矩形的較短邊與一條對(duì)角線的和的長(zhǎng)是12cm，則對(duì)角線的長(zhǎng)為_____cm，較長(zhǎng)的邊長(zhǎng)為______cm．