642
CHAPTER 10
PARAMETRIC EQUATIONS AND POLAR COORDINATES
25–27 U se the graphs of x � f �t� and y � t�t� to sketch the parametric curve x � f �t�, y � t�t�. Indicate with arrows the direction
in which the curve is traced as t increases.
19–22 D escribe the motion of a particle with position �x, y� as
t varies in the given interval.
19. x � 3 � 2 cos t,
y � 1 � 2 sin t, ��2 � t � 3��2
20. x � 2 sin t,
y � 4 � cos t,
21. x � 5 sin t,
y � 2 cos t,
x
25.
0 � t � 3��2
1
�� � t � 5�
1
y � cos2 t, �2� � t � 2�
22. x � sin t,
y � t�t�, where the range of f is �1, 4� and the range of t is
�2 , 3�. W hat can you say about the curve?
26.
y � t�t� in (a)– (d) with the parametric curves labeled I – IV.
G ive reasons for your choices.
I
y
y
1
1
1
1
y
1
1
t
27. x
2
t
x
1
24. M atch the graphs of the parametric equations x � f �t� and
x
2
t
1
t
1
t
_1
23. Suppose a curve is given by the parametric equations x � f �t�,
(a)
y
y
1
1
1
2 x
1 t
t
t
(b)
II
x
2
y
2
28. M atch the parametric equations with the graphs labeled I-V I.
y
2
1t
1t
(c)
G ive reasons for your choices. (D o not use a graphing device.)
(a) x � t 4 � t � 1, y � t 2
(b) x � t 2 � 2t, y � st
(c) x � sin 2t, y � sin�t � sin 2t�
(d) x � cos 5t, y � sin 2t
(e) x � t � sin 4t, y � t 2 � cos 3t
sin 2t
cos 2t
(f ) x �
, y�
4 � t2
4 � t2
2 x
III
x
2
y
y
1
2
2 t
I
III
y
y
2 x
1
2 t
II
y
x
x
x
(d)
IV
x
2
y
2 t
y
2
IV
2
V
y
VI
y
2 t
y
x
2 x
x
x