cos(π-θ)tan(3π+θ)/sin(π/2+θ)=3/4
(-cosθ)tanθ/cosθ=3/4
-tanθ=3/4
tanθ=-3/4
当θ为第二象限角时,cosθ=-4/5
当θ为第四象限角时,cosθ=4/5
cos(π-θ)tan(3π+θ)/sin(π/2+θ)=3/4,则cosθ=?
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