奇函數(shù)乘偶函數(shù)是奇函數(shù)，奇函數(shù)加減奇函數(shù)是奇函數(shù)，偶函數(shù)加減偶函數(shù)是偶函數(shù)，奇函數(shù)乘奇函數(shù)是偶函數(shù)，偶函數(shù)乘偶函數(shù)是偶函數(shù)。