作业帮cos方5π/12+cos方π/12+cosπ/12*cos5π/12 最后等于4/5的过程.
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cos方5π/12+cos方π/12+cosπ/12*cos5π/12 最后等于4/5的过程.
cos方5π/12+cos方π/12+cosπ/12*cos5π/12 最后等于4/5的过程.
cos方5π/12+cos方π/12+cosπ/12*cos5π/12 最后等于4/5的过程.
cos^2(π/4+π/6)+cos^2(π/4-π/6)+1/2[cos(5π/12+π/12)+cos(5π/12-π/12)]
=cos^2(π/4+π/6)+cos^2(π/4-π/6)+1/2[cos(π/2)+cosπ/3]
=2cos^2(π/4)cos^2(π/6)+2sin^2(π/4)sin^2(π/6)+1/4
=2*1/2*3/4+2*1/2*1/4+1/4
=5/4
cos方5π/12+cos方π/12+cosπ/12*cos5π/12
=cos方(π/2-π/12)+cos方π/12+cosπ/12*cos(π/2-π/12)
=sin方π/12+cos方π/12+cosπ/12*sinπ/12
=1+cosπ/12*sinπ/12
=1+1/2*sinπ/6
=1+1/2*1/2
=1+1/4
=5/4
cos方5π/12+cos方π/12+cosπ/12*cos5π/12 最后等于5/4的过程.
cos方5π/12+cos方π/12+cosπ/12*cos5π/12 最后等于4/5的过程.
cos方π/8-1/2
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