（1）sina+3cosa/sina-cosa=(tana+3)/(tana-1)=(2+3)/(2-1)=5（2）sin²a+sinacosa+3cos²a=(sin²a+sinacosa+3cos²a)/(sin²a+cos²a)=(tan²a+tana+3)/(tan²a+1)=(4+2+3)/(4+1)...