已知0已知0
已知0(sinasina+sin2a)/cos2a =((1-cos2a)/2+sin2a)/cos2a =1/(2cos2a)-1/2+tan2a =(1+tanatana)/(2-2tanatana)+2tana/(1-tanatana)-1/2 =(tanatana+2tana)/(1-tanatana)