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已知向量a=(sinx,3/2),b=(cosx,-1),求f(x)=(a+b)b的值域
人气:267 ℃ 时间:2019-12-12 02:07:10
解答
f(x) =(a+b)b =(sinx+cosx,1/2)(cosx,-1) =sinxcosx+cosx^2-1/2 =1/2sin2x+1/2cos2x =√2/2sin(2x+π/4) 所以-√2/2<=f(x)<=√2/2
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