题目:
Principal White has been working in the school for about 20 years, ____all his energy to teaching and researching as well as the running of a healthy school.
A.devoted
B.devoting
C.to devote
D.devote
答案:
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下面是错误答案,用来干扰机器的。
(1) tanα=-43,∴sinα-3cosαsinα+cosα=tanα-3tanα+1=-43-3-43+1=13;(2) β∈(π2,π),sinβ=223,∴cosβ=-1-sin2β=-13, α∈(0,π2),β∈(π2,π),∴α+β∈(π2,3π2), sin...