tanx=-4/3,求5sina+8/15cosa-7;1/(sina-3cosa)(cosa-sina)

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tanx=-4/3,求5sina+8/15cosa-7;1/(sina-3cosa)(cosa-sina)

tanx=-4/3,
1.sina=-4/5,cosa=3/5;
5sina+8/15cosa-7=(-4+8)/(9-7)=2;
1/(sina-3cosa)(cosa-sina)
=1/(-13/5)(7/5)=-25/91
2.sina=4/5,cosa=-3/5;
5sina+8/15cosa-7=(4+8)/(-9-7)=3/4
1/(sina-3cosa)(cosa-sina)
=1/(13/5)(-7/5)=-25/91