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- doraemonpaulLv 710 years agoFavorite Answer
只有在限定的條件下，tan才會有和差化積的公式，詳見

http://en.wikipedia.org/wiki/List_of_trigonometric...

2010-10-22 06:59:22 補充：

tan只有這條「所謂的和差化積公式」：

tan A + tan B – tan (A + B) = – tan A tan B tan (A + B)

參考資料：

formula from http://en.wikipedia.org/wiki/List_of_trigonometric... + my maths knowledge

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