One version of the Race Track Principle:
If two horses start a race at the same point, then the faster horse is always ahead.
If
and
for
, then
for
.
Put
and ![]()
and look at:
![[Graphics:Images/index_gr_8.gif]](Images/index_gr_8.gif)
![[Graphics:Images/index_gr_10.gif]](Images/index_gr_10.gif)
Use the Race Track Principle and what you see above to explain why
for ![]()
provided
.
Heavy Tip:
You are given that
.
This tells you that
![]()
so
Another version of the Race Track Principle:
If two horses start at the same point and they run at nearly the same speed for the whole race, then they run very close together all the way and are likely to end the race in a photo finish.
If
and
is nearly the same as
for
then
is nearly the same as
for
.
Now look at:
![[Graphics:Images/index_gr_25.gif]](Images/index_gr_25.gif)
![[Graphics:Images/index_gr_27.gif]](Images/index_gr_27.gif)
Both functions start their race at
together:
![[Graphics:Images/index_gr_30.gif]](Images/index_gr_30.gif)
Here's a plot of the instantaneous growth rates of both functions for
:
![[Graphics:Images/index_gr_33.gif]](Images/index_gr_33.gif)
![[Graphics:Images/index_gr_34.gif]](Images/index_gr_34.gif)
Use this plot and the Race Track Principle to determine
so that
and
are nearly the same for
.
Check yourself with a plot.
Here's another version of the Race Track Principle:
If two horses end the race in a dead heat, then the faster horse was behind all the time except at the finish line.
If
and
for
then
...........
for
.
Delete and fill in the blank above.
Go with
and
and look at:
![[Graphics:Images/index_gr_47.gif]](Images/index_gr_47.gif)
![[Graphics:Images/index_gr_49.gif]](Images/index_gr_49.gif)
Remembering that
spends all its life oscillating between
and
, use the Race Track Principle and what you see above to explain why
for
.
Another version of the Race Track Principle:
If two horses run at exactly the same speed for the whole race, and they are tied at one point of the race, then they are tied throughout the race.
Suppose
is one point with
and
and
for all
's with
;
then
.................
for
.
Delete and fill in the blank above.
Look at this:
![[Graphics:Images/index_gr_65.gif]](Images/index_gr_65.gif)
![[Graphics:Images/index_gr_67.gif]](Images/index_gr_67.gif)
![[Graphics:Images/index_gr_69.gif]](Images/index_gr_69.gif)
![[Graphics:Images/index_gr_71.gif]](Images/index_gr_71.gif)
Explain why this gives a calculus explanation of the identity
for all the
's.
Here's yet another version of the Race Track Principle:
If two horses run at exactly the same speed and at one point of the race one horse is
lengths ahead, then the same horse was
lengths ahead throughout the race.
Suppose
is one point and
and
for all
's;
then
..............
for all
's.
Fill in the blank above.
Look at this:
![[Graphics:Images/index_gr_83.gif]](Images/index_gr_83.gif)
![[Graphics:Images/index_gr_85.gif]](Images/index_gr_85.gif)
![[Graphics:Images/index_gr_87.gif]](Images/index_gr_87.gif)
![[Graphics:Images/index_gr_89.gif]](Images/index_gr_89.gif)
Explain why this gives a calculus explanation of the identity
for all the
's.