I am a senior three now, and I remember doing it with the knowledge of the unit circle when I was a freshman.

If point P is in the unit circle, the radius of the unit circle is 1, and A is the angle formed by op and X axis.

So the coordinates of point P can be expressed as (1*cosA, 1*sinA).

And |OP|= 1.

In the same way; In a similar way

When |OP|=2, that is, the radius of the unit circle is 2,

The point p is on the terminal edge of the angle (2π)/3,

So A=(2π)/3

So the coordinate of point P can be expressed as (2*cosA, 2*sinA).

That is, the coordinates of point P are (-1, and the root number is 3).

In the third year of high school, we will learn polar coordinates to solve problems.

If you don't understand, ask me (if you like).