1 . pai/3+2k pai & lt； = a & lt=5/pai+2kpai

The second question is a supplement to this one.

12 the first question is to say hello, and the second question is to prove that the tangent of A is longer than the arc corresponding to A by area method, and that A is smaller than tana, and similarly, A is larger than sina.

I'm exhausted ... I really can't. Ask me. Should be right.