如图,在4×5网格图中,其中每个小正方形边长均为1,梯形ABCD和五边形EFGHK的顶点均为小正方形的顶点.
(1)以B为位似中心,在网格图中作四边形A′BC′D′,使四边形A′BC′D′和梯形ABCD位似,且位似比为2:1;
(2)求(1)中四边形A′BC′D′与五边形EFGHK重叠部分的周长.(结果保留根号)
用方框中所给单词的适当形式填空,每词限用一次。
My parents are very ____ every day except weekends.If you don’t sleep well, you can drink some____ before you go to bed.She often____ a white dress. White is her favorite.Sussan cooked dinner for ____ when she studied in Canada.I have learned English for ____ 10 years and I’m very good at it.
(1)蜡烛在空气中燃烧时生成二氧化碳和水.由此判断蜡烛中一定含有的元素是____ (填元素符号).
(2)“84”消毒液可用于灾区防疫,其主要成分是次氯酸钠(NaClO),制取它的化学方程式为2NaOH+X═NaClO+NaCl+H2O,则X的化学式为 ____ .求出NaClO中氯元素化合价并在该化学式中表示出来 ____ .
(3)在反应A+3B=2C+2D中,14克A完全反应生成44克C和18克D,若A的相对分子质量为28,则B的相对分子质量是____ .