Question

请会的大哥大姐多多指教.已知sinθ=(√5-1)/4(1)求(sinθ-cosθ)/(sinθ+cosθ)+(sinθ

Answer 1

1)tg2θ=(6-2根5)/(10+2根号5) (tg后的2是平方,下面都是这样)

原式=(tgθ-1)/(tgθ+1)+(tgθ+1)(tgθ-1) 同除以cosθ

=2(tg2θ+1)/(tg2θ-1)

代入后得原式=2-2根号5

2)可知tgθ=-2.4,若θ在第二象限,则cosθ=-5/13,若θ在第四象限,则cosθ=5/13

cosθ=-5/13

原式=(9+tgθ)/(4/cosθ-6tgθ)=(9-2.4)/(-4/5/13+6*2.4)=1.65

cosθ=5/13

原式=(9+tgθ)/(4/cosθ-6tgθ)=(9-2.4)/(4/5/13+6*2.4)=33/124