该函数单调递减时,有:2kπ《-2x + π/4《2kπ + π (k是任意整数),
整理:-kπ - (3π/8)《 x《-kπ + (π/8),取它与[-π,π]的公共区间,
即得函数减区间:[-π,(-7π/8)]∪[(-3π/8),(π/8)]∪[(5π/8),π]
该函数单调递减时,有:2kπ《-2x + π/4《2kπ + π (k是任意整数),
整理:-kπ - (3π/8)《 x《-kπ + (π/8),取它与[-π,π]的公共区间,
即得函数减区间:[-π,(-7π/8)]∪[(-3π/8),(π/8)]∪[(5π/8),π]