求证:sinθ(1+cos2θ)=sin2θcosθ
证明:∵左边=sinθ•2cos2θ=(2sinθcosθ)cosθ=sin2θcosθ=右边,所以,原等式成立.
------Hey, Emily, I’ve got a used copy of our chemistry textbook for half price.
------ I’m afraid you ____ your money. Yours is the first edition, but we’re supposed to be using the third edition.
A.had wasted
B.were wasting
C.wasted
D.will waste
《消防法》规定矿井地下部分、海上石油天然气设施的消防工作,由()监督管理。
A.公安机关消防机构
B.省级人民政府
C.县级以上人民政府
D.其主管部门