What is the correlation between dr/dt of a vector formula ______i + ______j and dy/dx of its parametric equivalent of x=_____t and y=______t ?

For example in 3cos(t)i+3sin(t)j

This is confusing to me as I understand that one is taking the derivative of x with respect to y and one x and y both with respect to t, but graphically it makes no sense to me that there would be no correlation which is what my math teacher claims.