Answer:
[tex]\vec r = R(-cos\omega t \hat i + sin\omega t\hat j)[/tex]
Explanation:
Let say the particle starts in counterclockwise direction with constant angular speed
so the angle turned by the particle after some time is given as
[tex]\theta = \omega t[/tex]
now the x and y components of the position of the particle is given as
[tex]x = R sin\omega t[/tex]
[tex]y = R cos\omega t[/tex]
now we know that it starts in counter clockwise direction so we will have position vector given as
[tex]\vec r = x\hat i + y\hat j[/tex]
[tex]\vec r = R(-cos\omega t \hat i + sin\omega t\hat j)[/tex]