比较大小(1)sin194,cos160(2)sin7/4,cos5/3(3)cos(-47、10派）,cos(-44/9派）要过程
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(1)sin194=-sin14=-cos76
cos160=-cos20<-cos76
所以sin194>cos160
(2)sin7/4>0
cosπ>cos5/3>cos(π/2)=>cos5/3<0
所以sin7/4>cos5/3
(3)cos(-47π/10)=cos(-47π/10+4π)=cos(-7π/10)=cos(7π/10)=cos(63π/90)
cos(-44π/9)=cos(-44π/9+4π)=cos(-8π/9)=cos(8π/9)=cos(80π/90)<cos(63π/90)
所以cos(-47π/10)>cos(-44π/9)
cos160=-cos20<-cos76
所以sin194>cos160
(2)sin7/4>0
cosπ>cos5/3>cos(π/2)=>cos5/3<0
所以sin7/4>cos5/3
(3)cos(-47π/10)=cos(-47π/10+4π)=cos(-7π/10)=cos(7π/10)=cos(63π/90)
cos(-44π/9)=cos(-44π/9+4π)=cos(-8π/9)=cos(8π/9)=cos(80π/90)<cos(63π/90)
所以cos(-47π/10)>cos(-44π/9)
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