奇函數(shù)乘以奇函數(shù)等于偶函數(shù)。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)。偶函數(shù)乘偶函數(shù)是偶函數(shù)。