would apppeciate very much is anyone can help me in the below question. thanks.

A man runs round a circular track at a constant speed.
Would like to know how to drawn locus of the points representing the magnitude ‘d’ of the displacement of the man from the starting position against time ‘t’ , during one lap of the track.need to find the equation of the curve.

see the related questions below.

Think of polar coordinates, and place the starting point at (r,0)