cos2/15π+cos4/15π+cos8/15π+cos16/15π

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cos2/15π+cos4/15π+cos8/15π+cos16/15π
cos2/15π+cos4/15π+cos8/15π+cos16/15π

cos2/15π+cos4/15π+cos8/15π+cos16/15π
cos(2π/15)+cos(4π/15)+cos(8π/15)+cos(16π/15)
=2cos(9π/15)cos(7π/15)+2cos(6π/15)cos(6π/15)cos(2π/15)
=2cos(3π/5)*[cos(7π/15)-cos(2π/15)]
=-4cos(3π/5)sin(3π/10)sin(π/6)
=-2cos(3π/5)sin(3π/10)

cos2/15π+cos4/15π+cos8/15π+cos16/15π 计算：cosπ/15×cos2π/15×cos4π/15×cos8π/15 cos2/7π*cos4/7π*cos6/7π=? 求值：cos2π/7 * cos4π/7 * cos6π/7 cosπ/9*cos2π/9*cos4π/9=? 求值cos2π/9*cos4π/9*8π/9 cosπ/7cos2/7πcos4/7π= 求值:cos2π/7cos4π/7cos8π/7 cos2π/7+cos4π/7+6π/7= cos2π/7cos4π/7cos6π/7=? cos2π/7+cos4π/7+cos6π/7= 求值cos2π/9cos4π/9cos8π/9 cos2/7π+cos4/7π+cos6/7= cosπ/15 cos2π/15 cos3π/15 cos4π/15 cos5π/15 cos6π/15 cos7π/15他们都相乘求等于多少化简cosπ/9*cos2π/9*cos3π/9*cos4π/9 求cosπ/9*cos2π/9*cos3π/9*cos4π/9 化简sin π/7(cos2π/7+cos4π/7+cos6π/7) cos1/5π+cos2/5π+cos3/5π+cos4/5π=多少