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已知: f(α)= sin(−α)cos(π+α)cos( π 2 −α) cos(π−α)sin(2π+α)tan(π+α) (1)化简f(α); (2)若角α的终边在第二象限且 sinα= 3 5 ,求f(α).

已知: f(α)= sin(−α)cos(π+α)cos( π 2 −α) cos(π−α)sin(2π+α)tan(π+α) (1)化简f(α); (2)若角α的终边在第二象限且 sinα= 3 5 ,求f(α).

已知:f(α)=sin(−α)cos(π+α)cos(π2−α)cos(π−α)sin(2π+α)tan(π+α)(1)化简f(α);(2)若角α的终边在第二象限且sinα=35,求f(α).

(1)f(α)=

=-

=-cosα;

(2)由题意:cosα=−

=−

,∴f(α)=−cosα=