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).
的有关信息介绍如下: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=
.