化简f(X)=(1-√2sin(2X-π/4))/cosX
问题描述:
化简f(X)=(1-√2sin(2X-π/4))/cosX
答
f(X)=(1-√2sin(2X-π/4))/cosX=[1-√2(sin2x*cosπ/4-cosx*sinπ/4)]/cosx=(1-sin2x+cos2x)/cosx=(1-sin2x+2(cosx)^2-1)/cosx=(2(cosx)^2-2sinxcosx)/cosx=2cosx(cosx-sinx)/cosx=2(cosx-sinx)或者再简化=2...设α为第四象限角,且tanα=﹣4/3,求f(α)的值α为第四象限角,则sinα0tanα=﹣4/3,由1+(tanα)^2=1+16/9=25/9=1/(cosα)^2,则cosα=3/5, sinα=-4/5f(α)=2*7/5=14/5由1+(tanα)^2=1+16/9=25/9=1/(cosα)^2则cosα=3/5, sinα=-4/5 怎么得来的???是tanx和cosx的关系式呀 看图