向量积为零

bicycle repair是什么意思 Moist repair 在⊿ABC中,AD是BC边上的高,BE是AC边上的高,AD,BE相交于F,连接CF,且AC=BF,求证∠ABC+∠FCD=90度. 三角形ABC中,AD是BC上的高,BE是AC上的高,AD,BE相交点F,联CF,且AC=BF,判断角ABC,角FCB的关系说明? 英语翻译 承诺 A PROMISE怎么样 请直译以下几句话,不要意译.Monthly ReportProvisional estimates Final estimatesNotes)Figures may not add up to the totals because of rounding.Based on the 2010 Populations Census,Final estimates for this month's population will be computed 英语翻译 一种药水,粉和水的比是三比100,要配置药水618克需要药粉多少千克? I regretted saying it almost at once这句话是什么时态呀? I regretted saying it almost at once.为什么用saying almost all his friends suggested ----Mr.Johnson at onceA.that he visits B.to him to visit C.that he visit D.to him for visiting 一种药水按药粉和水的比3:100配制而成.（1）要配制药水618克,需药粉多少千克?（2）用9一种药水按药粉和水的比3:100配制而成.（1）要配制药水618克,需药粉多少千克?（2）用900克水配这种药水, 现在学经商好学吗?好学吗 I'd been saying this lie so frequently lately that it sounded almost convincing now.so frequently lately 三个副词?that it sounded almost convincing now是哪类从句? Someday,someone will best me.But it won't be today,and it won't be you.求出处!RT 一个正方形分成两个小长方形,它们的周长的和（ ）正方形的周长.A大于.B小于.C等于一个正方形分成两个小长方形,它们的周长的和（ ）正方形的周长.A大于.B小于.C等于 Explain the meaning of SI base units and SI derived units用英文回答 what's SI units of energy and power?谁能给我问题上面的详细单位,以及它们的符号? 虚区伪和假装有什么别? 阅读垂老别,1）“垂老不得安” 安------2) "纵死时犹宽" 纵------3）“忆昔少壮日” 昔-------4）“烽火被冈峦 ”烽火------ 我数学不好,现在做生意 报价总是没个底,希望有经验的大哥大姐请教一下,比喻这个货我拿来是5块钱 我现在是翻3倍 也就是买15块,但是这个货如果要50块 我再翻3倍 150块 太高了 ,这里面有没有 “问渠那得清如许?为有源头活水来.”这两句诗句怎么翻译? The traffic had started to move more freely and Jim （ ）to the bus shelter at the roaside ,and waited.A.was walking B.had walkedC.would walk D.walked 不理解语法The molecules of gases move more freely than do those of liquids and solids.这句干吗要把 do 提前呢,如果这样说The molecules of gases move more freely than those of liquids and solids do. 甲乙两人合作做生意,甲支出8w,乙支出5w,总收入20w,请问甲乙两人分得的利润应各是多少?怎样分才公平? greater和advantage什么意思/ 英语翻译 一个奇怪的问题,工钱分配,数学问题.朋友让我帮算：甲乙两人合伙包工,共收入400元,甲干了0.5天,乙干了1.5天.甲乙工作熟练度不同,协商决定甲按45%,乙55%的比例分配.如何分? silence infection是什么意思?英语高手请进,要真知道这个词的意思啊,不要只是猜,它是一个医学术语 请问失声的英文单词是什么?是Silence吗? Silence情つ请问这个单词是什么意思?3Q