2022英语周报七年级YCS答案

a=√3,11.解:(1)由题意得a2+b=2、b2b=2所以:x)=√3sing-cosx又因为(2)=2n(x一5)∈[2x],所以当x=π时,f(x)取得最小值是1(8分)(2)法一:由题得asin2x- SIn cos+a>0对x∈(o2)恒成立,dU a(1-cos 2x)-sin 2x+2a>0,即3a>sin2x+acos2x恒成立,所以3a>√a2+1,解得a>y2,故实数a的取值范圈是(,+∞)(20分)法二:利用分离变量法可得,只要a>2恒成立,即求y=5m2x+1的最大值tan因为y=sm2x+1=2m2x+c03x=2an2x+1,令nx=t(t>0),t+y=22+12t+-利用单调性易得函数u=2+的最小值为2√2,则1≤=y,所以2+12√2故实数a的取值范圄是(2,+∞(20分)

One possible versionThe Most Beautiful Place in My HeartAs a 17-year-ol teenager, I ve been to many great cities, among which Luoyang is the most beautiful one inlocated on the north bank of the luo river in western Henan pruvinee l aovany is surrounded by mountains on threesidles, high in the west and low in the east. At the end of 2019, Luoyang had a population of more than 7. I millionI love Luoyang so much due to the fact that as one of the four ancient capitals of China, Luoyang has a civilizationhistory of 5, 000 years. Whats more, the number of its heritage sites is second only to Beijing in cities of China. And itfamous tourist attractions inelude Lungmen Grottoes, Baima Temple, Guanlin and so on

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