求值:log2(cosπ/9)+log2(cos(2π)/9)+log2(cos(4π)/9)log后的2为下标,

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求值:log2(cosπ/9)+log2(cos(2π)/9)+log2(cos(4π)/9)log后的2为下标,求值:log2(cosπ/9)+log2(cos(2π)/9)+log2(cos(4π

求值:log2(cosπ/9)+log2(cos(2π)/9)+log2(cos(4π)/9)log后的2为下标,
求值:log2(cosπ/9)+log2(cos(2π)/9)+log2(cos(4π)/9)
log后的2为下标,

求值:log2(cosπ/9)+log2(cos(2π)/9)+log2(cos(4π)/9)log后的2为下标,
log2(cosπ/9)+log2(cos(2π)/9)+log2(cos(4π)/9
==log2(cosπ/9*cos2π/9*cos4π/9)
==log2[(2sinπ/9*cosπ/9*cos2π/9*cos4π/9)/2sinπ/9]
==log2[(sin2π*cos2π/9*cos4π/9)/2sinπ/9]
==log2[(sin4π/9*cos4π/9)/4sinπ/9]
==log2[(sin8π/9)/(8sinπ/9)]
==-3