f(x)=2sin(2x+n)+m

Substitute the coordinates of point m

f(2π/3)=-2+m=- 1

So m= 1.

And because when x=2π/3, f(x)=- 1.

So n=π/6

f(x)=2sin(2x+n)+ 1

(2) According to the title,

sin(2a+π/6)=- 1/3

So sina/2+cosa/2 radical number 3=- 1/ radical number 3.

Because of the value range of a

Root number 3cosa/2-Sina/2 =- (root number 2)/3

I add up the two types.

Cosa=(- root number 3-2 root number 2)/2 root number 3