问题
选择题
函数f(x)=sin(πcosx)在区间[0,2π]上的零点个数是( )
A．3
B．4
C．5
D．6
答案
答案：C
f(x)=sin(πcosx)=0,
则πcosx=kπ(k∈Z),cosx=k(k∈Z),
∴cosx=±1或cosx=0,
又x∈[0,2π],
则x=0或x=π或x=2π或x=
或x=
,
即有5个零点.故选C.
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函数f(x)=sin(πcosx)在区间[0,2π]上的零点个数是( )
A．3
B．4
C．5
D．6
答案：C
f(x)=sin(πcosx)=0,
则πcosx=kπ(k∈Z),cosx=k(k∈Z),
∴cosx=±1或cosx=0,
又x∈[0,2π],
则x=0或x=π或x=2π或x=或x=,
即有5个零点.故选C.
Last spring, I was fortunate to be chosen to participate in an exchange study program. In my application letter, I was careful to ____ how much I wanted to see France; evidently, my excitement really came through in my words. Once I ____ that I was going, all I could think about was the fun of foreign travel and making all sorts of new and ____ friends. While traveling was inspiring and meeting people was ____， nothing about my term in France was what I ____. The moment I arrived in Paris, I was ____ by a nice French couple who would become my host parents. My entire experience was joyous and exciting ____ I received some shocking news from my program coordinator(协调人): there had been a death in my host parents' extended family. They had to travel outside France for several weeks. That afternoon, I had to ____ out of one family's house and into another. The exchange coordinator told me I'd have a ____ this time and asked whether I could share a bedroom with an English speaker. To avoid the temptation(诱惑) to ____ my native language, I asked not to be ____ with an Englishspeaking roommate. When I got to my new room, I ____ myself to my new roommate Paolo, a Brazilian(巴西人) the same age as I, whom I was surprised to find playing one of my favorite CDs! In just a few hours, we knew we'd be good friends for the rest of the ____. I left France with many ____， so when people ask me what my favorite part of the trip was, they are always ____ to hear me talk about my Brazilian friend Paolo and the scores of weekdays in class, weeknights on the town, and weekends ____ France we enjoyed together. I love how people ____ seem so different, but end up being so ____. The most valuable lesson I gained from studying in France wasn't just to respect the French people ____ to respect all people，for your next best friend could be just a continent away. I would recommend an exchange program to anyone who wants to experience foreign cultures and gain meaningful ____.
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