为什么是∵x∈【0,π/2】∴2x-π/4∈[-π/4,3π/4]
1个回答
∵x∈[0,π/2] 两边同乘以2
∴2x∈[0,π] 两边同减去π/4
∴2x-π/4∈[0-π/4,π-π/4]=[-π/4,3π/4]
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