sin(arccos1/4)=?
0
0

2个回答

  • 令 x =arccos (1/4),

    则 x ∈(0,π),

    且 cos x =1/4.

    所以 sin x =√ [ 1 -(cos x)^2 ]

    = √15 /4.

    即 sin [ arccos (1/4) ] = √15 /4.

    = = = = = = = = =

    换元法.

    注意 f(u) =arccos u 的值域.

    arccos

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