Hi, I had trouble with Qn94 c,d)For (c), Why is the answer the set {k pi for k in integer} intersect {pi/6 +kpi/3} And pi/2 and 3pi/2 for (d) ?Could someone explain how to get the set of values for cusp?

Differentiating Parametric Functions Q93. Velocity, speed and acceleration. For each of the following parametric curves r : R - R2, find formulas for the velocity, speed and acceleration at time t. (a) r(t) = cos(t)i + sin(3t)j. (b) r(t ) = thi+ +7j. (c) r(t) = e-ti+ +3j. (d) r(t) = e-bite-j