Is someone here willing to help me with trigonometry

I will post the problem which im having trouble with if someone will help. The reason why im not posting it yet is because I doubt someone will actually help. And the way I'm gonna proof check that you aren't trolling is by checking your explanation. So don't even try to troll me with the wrong answer. I have the answer for the question but I don't know how it is right. I am trying to see the explanation it gave but it is confusing. Will anyone help?

sure I'll help

What's the problem? I doubt I can help, but I'll try. 

Im in 7th grade so im not that much into it but I know the basic fundamentals

Trigonometry is very importantin China. I think in America it is very important too. So study hard

Here is the problem:

The angle is in radians. There is one step in solving it that I don't understand. This isn't the exact problem, but they all are similar.

for that specific equation, I think it would probably be like √3/3 since the first step is dividing  4π/3 by the same thing which would be -1/2 over - √3/2 which would be 1/√3 multiplied with √3/√3 after you cancel out the 2s which would equal to √3/3. I haven't done too much of this but this is from what I know.

just curious, what grade are you in?

I legit solved it lol

Oh lol I was too lazy to read the comments

Oh nvm I solved it. I understand it now.

Honestly, I feel like you posted this thread solely to boast that you are doing trigonometry-level math at the age of twelve...

I agree lol, at least i was able to solve it! (I think at least xD)

well that's another way to see it

Ok I know how to solve it, now I have another problem. Why is this useful and why does it work? What is the true use of sine? What is the true meaning of all this? Why is it when you have this angle that this is the coordinate of the point where it intersects the unit circle? Why is the point (x,y) which means (cosine,sine)?

I mean, it is a decent thing to brag about, I guess.

As for why trigonometric ratios are useful for practical purposes, they play a role in the physics concepts of dynamics, kinematics, and calculating vectors. As for why it works, sine, cosine, tangent, and cotangent are all just numbers — ratios to be exact and they all represent specific ratios of side lengths of a right triangle. 

did you search that up lol