求值(2cos(π/9)+1)tan(2π/9)-2sin(π/9)

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求值(2cos(π/9)+1)tan(2π/9)-2sin(π/9)求值(2cos(π/9)+1)tan(2π/9)-2sin(π/9)求值(2cos(π/9)+1)tan(2π/9)-2sin(π/

求值(2cos(π/9)+1)tan(2π/9)-2sin(π/9)
求值(2cos(π/9)+1)tan(2π/9)-2sin(π/9)

求值(2cos(π/9)+1)tan(2π/9)-2sin(π/9)
1=2cos(π/3)
所以原式=(2cos(π/9) + 2cos(π/3)) * tan(2π/9) - 2sin(π/9)
=(和差化积)=4cos(2π/9) * cos(π/9) * tan(2π/9) - 2sin(π/9)
=4sin(2π/9) * cos(π/9) - 2sin(π/9)
=(积化和差)= 2sin(π/3) + 2sin(π/9) - 2sin(π/9)
=2sin(π/3) = √3

值是0.0243