posted by Joe .
Ok I know that the slope of a straight line is the same thing as x with a dot aboce it or simply the first derivative of x
on the unit circle tangent gives you the slope of the reference line right? This can be expressed using the notation expressed above but how?
x with a dot above it usually represents the derivative with respect to time.
I don't know what you mean by "the reference line" or "the notation expressed above". I also don't see what unit circle is involved.