(3)
在(2)的條件下,若射線DA繞點(diǎn)D順時(shí)針旋轉(zhuǎn)至DO后立即回轉(zhuǎn),射線EO繞點(diǎn)E順時(shí)針旋轉(zhuǎn)至ED停止,射線DA轉(zhuǎn)動(dòng)的速度是4°/秒,射線EO轉(zhuǎn)動(dòng)的速度是1°/秒.若射線DA先旋轉(zhuǎn)4秒,射線EO才開(kāi)始繞點(diǎn)E順時(shí)針旋轉(zhuǎn),在射線EO到達(dá)ED之前,射線EO旋轉(zhuǎn)到第幾秒時(shí),射線DA與射線EO互相平行,直接寫(xiě)出答案.