23.如圖1,點(diǎn)O是菱形ABCD對(duì)角線的交點(diǎn),已知菱形的邊長(zhǎng)為12,∠ABC=60°.
(1)求BD的長(zhǎng);
(2)如圖2,點(diǎn)E是菱形邊上的動(dòng)點(diǎn),連接EO并延長(zhǎng)交對(duì)邊于點(diǎn)G,將射線OE繞點(diǎn)O順時(shí)針旋轉(zhuǎn)30°交菱形于點(diǎn)H,延長(zhǎng)HO交對(duì)邊于點(diǎn)F.
①求證:四邊形EFGH是平行四邊形;
②若動(dòng)點(diǎn)E從點(diǎn)B出發(fā),以每秒1個(gè)單位長(zhǎng)度沿B→A→D的方向在BA和AD上運(yùn)動(dòng),設(shè)點(diǎn)E運(yùn)動(dòng)的時(shí)間為t,當(dāng)t為何值時(shí),四邊形EFGH為矩形.