已知f(α)=(tan(π-α)*cos(2π-α)*sin(二分之π+α))/(cos(-α-π)) (1)化简f(α)

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已知f(α)=(tan(π-α)*cos(2π-α)*sin(二分之π+α))/(cos(-α-π)) (1)化简f(α)

f(α)=(tan(π-α)*cos(2π-α)*sin(二分之π+α))/(cos(-α-π))
=-tana*cos(-α)*cosa/(-cosa)
=tana*cosα*cosa/cosa
=sina
应用诱导公式奇变偶不变,符号看象限