1. The graphs in the left column are simultaneous cartesian graphs of two functions x = x(t), y = y(t)for t in an interval [a, b]. The parametric curves C: (x, y)=(x(t), y(t)) of these pairs are on the right. Match the graphs on the right with those on the left. Then using arrows, indicate how the parametric curve is traced out as t increases on its domain

 

A

I

B

II

C

III

D

IV

E

V

Solution:

Start with B. All the values of x and y are ³ 0 so the parametric graph will be in the first quadrant. Graph IV is the only one on the right that has this property, so B corresponds to IV.

In D all the y values are ³ 0 so D corresponds to II

In E, dx/dt = 0 (without dy/dt being 0) 3 times so the corresponding parametric curve has 3 vertical tangent. So E corresponds to III

In A dx/dt = 0 (without dy/dt being 0) 2 times si the matching parametric curve has 2 vertical tangents. So A corrsponds to V

By elimimation C corresonds to I.

 

The "paths traveled are indicated below