Mathematics

Problem

At any two points of the curve represented parametrically by

x = a(2 \cos t - \cos 2t)

and

y = a(2 \sin t - \sin 2t)

, the tangents are parallel to the axis of

x

corresponding to the values of the parameter

t

differing from each other by (a)

2\pi/3

(b)

3\pi/4

(c)

\pi/2

(d)

\pi/3