(3sina-cosa)/(sina+2cosa)
=(3tana-1)/(tana+2)
=(3*2-1)/(2+2)
=5/4
2/3 sin²a+1/4cos²a
=(2/3tan²a+1/4)*cos²a
=(2/3*2+1/4)*1/(1+tan²a)
=19/4*1/(1+4)
=19/20
2sin²a-sina*cosa+cos²a
=(2tan²a-tana+1)cos²x
=(2*2-2+1)*1/(1+tan²a)
=3*1/(1+4)
=3/5