解∵sina∈[-1,1],cosa∈[-1,1]∴sina+cosa∈[-2,2]∴sina+cosa≠-3∵(tana-3)(sina+cosa+3)=0∴tana-3=0,或sina+cosa+3=0∴tana=3或sina+cosa=-3（舍去）2/3sin²a+1/4cos²a=(2/3sin²a+1/4cos²a...