What do you mean by the choice of compulsory four in senior high school mathematics and the condition that angle α is less than O? The correct answer is a.
This question is multiple choice. According to the branch option, there is only one answer.
Cunning method
Solution a > 0
R=/OP/=5a。
Then sina=y/r=4a/5a=4/5.
cosa=x/r=-3a/5a=-3/5
So Sina +2cosa=-2/5.