如果/cosx?
如果/cosx/=cos(-x+π),则x的取值范围
cos(-x+π)=-cos(-x)=-cosx。|cosx|=-cosx,则cosx≤0,得2kπ+π/2≤x≤2kπ+3π/2,k∈Z
问:取值范围已知向量a=(sinx,0),b=(cosx,1)其中0<x<2π/3,求|(1/2)a-(√3/2)b|的取值范围
答:解: `|a/2-√3·b/2|=|(sinx/2,0)-(√3·cosx/2+√3/2)| =|sinx/2-√3·cosx/2-√3/2| =|sin(x-...详情>>
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