tana/2=2
tana
=2tan(a/2)/(1-tan^2(a/2))
=2*2/(1-4)
=-4/3
(1)
tan(a+π/4)
=(tana+tanπ/4)/(1-tana*tanπ/4)
=(tana+1)/(1-tana)
=(-1/3)/(7/3)
=-1/7
(2)
(sin2α-cos^2α)/(1+cos2α)
= (2sinαcosα-cos^2α)/(1+2cos^2α-1)
= (2sinαcosα-cos^2α)/(2cos^2α)
= tanα-1/2
=-4/3-1/2
=-11/6tanα－1/2是怎么来的(2sinαcosα-cos^2α)/(2cos^2α)上下同除2cos^2α=tanα－1/2我这个设备点不到好评怎么办点击选为满意答案