iauder220 wrote:若3tan(2a)=5sec(a)-1,則sec(a)=?太久沒接觸了,所以忘記該怎麼算,煩請大家幫忙一下,謝謝!! 版主題目沒寫錯吧?應該是3tan^2(a)=5sec(a)-1,則sec(a)=?答案請看http://answers.yahoo.com/question/index?qid=20100301065522AAAxL9e