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內(nèi)偶則偶，內(nèi)奇同外。偶函數(shù)±偶函數(shù)=偶函數(shù)；奇函數(shù)×奇函數(shù)=偶函數(shù)；偶函數(shù)×偶函數(shù)=偶函數(shù)；奇函數(shù)×偶函數(shù)=奇函數(shù)。函數(shù)的奇偶性推斷方