Rút gọn P = tan1 . tan2 . tan3 ... tan87 . tan88 . tan89.
Rút gọn P = tan1 . tan2 . tan3 ... tan87 . tan88 . tan89.
Lời giải
Ta có: tan α = cot (90° – α)
S = tan1° . tan89° . tan2° . tan88° ... tan44° . tan46° . tan45°
= tan1° . cot1° . tan2° . cot2° ... tan44° . cot44° . tan45°
= 1.1.1...1.1 = 1.