已知cos(α+β)=45,cos(a-β)=-45,则cosαcosβ的值为(

题型:选择题

问题:

已知cos(α+β)=
4
5
,cos(a-β)=-
4
5
,则cosαcosβ的值为(  )
A.0B.
4
5
C.0或
4
5
D.0或±
4
5
考点:两角和与差的三角函数及三角恒等变换
题型:选择题

People are indulging in an illusion whenever they find themselves explaining at a cocktail (鸡尾酒) party, say, that they are "in computers," or "in telecommunications," or "in electronic funds transfer". The implication is that they are part of the high-tech world. Just between US, they usually aren’t. The researchers who made fundamental breakthroughs in those areas are in a high-tech business. The rest of us are ()of their work. We use computers and other new technology components to develop our products or to organize our affairs. Because we go about this work in teams and projects and other tightly knit working groups(紧密联系在一起的工作小组), we are mostly in the human communication business. Our successes stem from good human interactions by all participants in the effort, and our failures stem from poor human interactions.

The main reason we tend to focus on the()rather than the human side of the work is not because it’s more (), but because it’s easier to do. Getting the new disk drive installed is positively trivial compared to figuring out why Horace is in a blue funk (恐惧) or why Susan is dissatisfied with the company after only a few months. Human interactions are complicated and never very crisp (干脆的, 干净利落的) and clean in their effects, but they matter more than any other aspect of the work.

If you find yourself concentrating on the()rather than the (), you’re like the vaudeville character (杂耍人物) who loses his keys on a dark street and looks for them on the adjacent street because, as he explains, "The light is better there!".

rather than the()

A.technology

B.sociology

C.physiology

D.astronomy

题型:选择题

关于糖浆剂的说法错误的是

A.可作矫味剂,助悬剂

B.糖浆剂为高分子溶液

C.热溶法制备有溶解快,滤速快,可以杀灭微生物等优点

D.蔗糖浓度高时渗透压大,微生物的繁殖受到抑制

E.可加适量乙醇、甘油作稳定剂

题型:选择题

PC-160型泡沫车是泡沫钻井的六大部件之一。

题型:选择题

一足月儿,母乳喂养,生后3天因黄疸住院,血清总胆红素289μmol/L,母血型为O型、Rh阳性,父亲血型为AB型、Rh阳性,首先应做哪项检查()

A.血培养

B.肝功能

C.血涂片找球形红细胞

D.定血型

E.抗人球蛋白试验

题型:选择题

宗教信仰自由政策的主要内容是什么?()

A、每个公民既有信仰宗教的自由,也有不信仰宗教的自由

B、有信仰这种宗教的自由,也有信仰那种宗教的自由

C、在同一宗教里面,有信仰这个教派的自由,也有信仰那个教派的自由

D、有过去不信教而现在信教的自由,也有过去信教而现在不信教的自由

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