计算:2cos(-660°)-sin630°/4cos1020°+2cos(-300°)

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计算:2cos(-660°)-sin630°/4cos1020°+2cos(-300°)计算:2cos(-660°)-sin630°/4cos1020°+2cos(-300°)计算:2cos(-660

计算:2cos(-660°)-sin630°/4cos1020°+2cos(-300°)
计算:2cos(-660°)-sin630°/4cos1020°+2cos(-300°)

计算:2cos(-660°)-sin630°/4cos1020°+2cos(-300°)
[2cos(-660°)-sin630°]/[4cos1020°+2cos(-300°)]
=[2cos(-720+60)-sin(720-90)]/[4cos(720+300)+2cos300]
=(2cos60+sin90)/(4coos300+2cos33)
=(2cos60+1)/6cos60
=2/3
sinα=sin(±360n+α)
sin(-a)=-sina
cos(-a)=cosa
sin90=1