cos2分之19π等于什么?

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cos2分之19π等于什么?
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cos2分之19π等于什么?
cos2分之19π等于什么?

cos2分之19π等于什么?

cos(19π/2)
=cos(10π-π/2)
=cos(-π/2)
=cosπ/2
=0

cos(2分之19π)
= cos(8π + 3π/2)
= cos(3π/2)
= 0

答:
cos2分之19π
=cos(19π/2)
=cos(10π-π/2)
=cos(-π/2)
=0

cos(8π+3/2π)
=cos(3/2π)=0