T=π (2x+π/4) monotonically increases on (2kπ-π/2, 2kπ+π/2).

Because X is monotonically increasing when it belongs to (kπ-3π/8, kπ+π/8)(k belongs to Z).

When (2x+π/4) belongs to (2kπ+π/2, 2kπ+3π/2), it monotonically decreases.

Because X is monotonically decreasing when it belongs to (kπ+π/8, kπ+5π/8)(k belongs to Z).

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