Выражение ( sin(30 + a) - cos(60+a))/(sin(30 + a) + cos(60+a))

=(sin(30)cosa+cos(30)sina-cos(60)cosa+sin(30)sina)/(sin(30)cosa+cos(30)sina+cos(60)cosa-sin(30)sina)=((1/2)cosa+(√3/2)sina-(1/2)cosa+(√3/2)sina)/((1/2)cosa+(√3/2)sina+(1/2)cosa-(√3/2)sina)=√3sina/cosa= √3tga