
Examples of Control Problems 11
Thus, the time of traverse T along C is given by
T =
1
(2g)
1/2
Z
x
1
x
0
1 + (y
′
)
2
y − α
1/2
dx.
The problem of finding a curve C that minimizes the time of traverse is
that of finding a function y = y(x) that minimizes the integ ral
Z
x
1
x
0
1 + (y
′
)
2
y − α
1/2
dx. (1.6.3)
Note that if v
0
= 0, then the integral is improper.
We put this problem in a format similar to the previous ones as follows.
Change the notation for the independent variable fr om x to t. Then set
y
′
= u y(t
0
) = y
0
. (1.6.4)
A continuous function u will be called admissible if it is defined on [t
0
, t
1
],
if the solution of (1.6.4) corresponding to u satisfies y(t
1
) = y
1
,