tan(7π+α)=tan(6π+(π+α))=tan(π+α)=tanα
sin(α-3π)+cos(π-α)/sin(-α)-cos(π+α)
=sin(-(3π-a))-cosα/(-sinα)+cosα
=-sin(3π-α)-cosα/(-sinα)+cosα
=sinα-cosα/-(sinα-cosα)
=-1
tan(7π+α)=tan(6π+(π+α))=tan(π+α)=tanα
sin(α-3π)+cos(π-α)/sin(-α)-cos(π+α)
=sin(-(3π-a))-cosα/(-sinα)+cosα
=-sin(3π-α)-cosα/(-sinα)+cosα
=sinα-cosα/-(sinα-cosα)
=-1