上下乘16sinπ/9sin2π/9sin3π/9sin4π/9原式=(2sinπ/9cosπ/9)(2sin2π/9cos2π/9)(2sin3π/9cos3π/9)(2sin4π/9cos4π/9)/(1616sinπ/9sin2π/9sin3π/9sin4π/9)=sin2π/9sin4π/9sin6π/9sin8π/9/(1616sinπ...