原式=log2(cosπ/9cos2π/9cos4π/9)
=log2(sinπ/9cosπ/9cos2π/9cos4π/9)/(sinπ/9)
=log2(sin2π/9cos2π/9cos4π/9)/(2sinπ/9)
=log2(sin4π/9cos4π/9)/(4sinπ/9)
=log2(sin8π/9)/(8sinπ/9)
求值!log2(cos湃/9)+log2(cos2湃/9)+log2(cos4湃/9)答案是-3,『湃就是3.14159
原式=log2(cosπ/9cos2π/9cos4π/9)
=log2(sinπ/9cosπ/9cos2π/9cos4π/9)/(sinπ/9)
=log2(sin2π/9cos2π/9cos4π/9)/(2sinπ/9)
=log2(sin4π/9cos4π/9)/(4sinπ/9)
=log2(sin8π/9)/(8sinπ/9)