如图，在⊙O中，OA＝AB，OC⊥AB，则下列结论正确的是（ ） ①．弦AB的长等于圆内接正六边形的边长 ②．弦AC的长等于圆内接正十二边形的边长
有一种白色粉末由等质量的两种物质混合而成，分别取适量该白色粉末置于三支试管中进行实验。 （1）逐滴加入6mol·L-1盐酸，同时不断振荡试管，有气
One sentence from the news in Washington has remained in my mind since a trip last summer: “When you see people run against the crowd escaping 61 the danger, they are 62 (probable)
已知平面向量,且,则实数的值为_________.
一艘观光游船从港口A处以北偏东60°的方向出港观光，航行80海里至C处时发生了侧翻沉船事故，立即发出了求救信号．一艘在港口正东方向B处的海警船
阅读表达。 Greenwood Park is the best place to go to on weekends. I always finish my breakfast fastest on Saturdays because I want to get to Greenwood Park before 10:00 a.m. to meet my friend
