1.函數(shù)y=2|cosx|的單調(diào)遞減區(qū)間是?
把y=2cosx圖像x軸下面的翻到x的上面
所以遞增區(qū)間為[-π/2+2kπ,2kπ]
遞減區(qū)間為[2kπ,2kπ+π/2]
2.使函數(shù)y=sin(π/6-2x)(x∈[0,π]為增函數(shù)的區(qū)間
如是y=sin(π/6-2x)為增函數(shù)
y=sin(2x-π/6)為減函數(shù)
2x-π/6∈[π/2+2kπ,3π/2+2kπ]
x∈[π/3+kπ,5π/6+kπ]
當(dāng)k=0時(shí),x∈〔π／3,5π／6〕
選C