tan(3x)證明 3tanx-tan^3x------------------ = tan3X 1-3tan^2x 這是證明題tan2x+tanx---------------------- <=Tan (2x+x) <= Tan3x1-(tan2x)(tanx)Tan^3X = 3 power of Tanx <=== 忘了中文怎講 抱歉.. link...