2kπ+π/2≤2x-π/4≤2kπ+3π/22kπ+π/2+π/4 ≤ 2x ≤ 2kπ+3π/2+π/42kπ+3π/4 ≤ 2x ≤ 2kπ+7π/4kπ+3π/8 ≤ x ≤ kπ+7π/8
孩子，加油脑子是自已的
