Substitute the above formula and sort it out.

Solve.

The coordinates of this point are, and its polar coordinates are.

(ii) Assume that the equation of the straight line l' is:

The curve c obtained by (i) is a circle with the center as the center, and the distance from the center to the straight line is,

Then, the solution, or,

Is the equation of a straight line, or,?

Its polar coordinate equation is.