Vector Summations - HP 25 Owner's Handbook Manual

70 Funclon K-
The correct values for mean and stand ard deviation are now
obtainable by pressing
[Xl
and
~ .
For example, suppose the 62-year old member of the sample
as given above were to lose his position as one of the wealthiest
persons because of a series of ill-advised investments in cocoa
futures. To account for the change in data if he were replace d
in the sample by a 21-year old rock musician :
Press
62
D ~
21
Ell
Display
62.
9.00
21.
10.00
Data to be replaced .
Number of entries
(n)
is now nine.
The new data.
Number of entries
(n)
is ten aga in .
The new data has been calculated into each of the summations
present in the storage registers. To see the new mean and
standard deviation :
Press
D@
DO
Display
60.30
17.09
The new average (mean) age .
The new standard deviation .
Vector Summations
The
Ell
key can be used to sum any quantities that are in the
x-
and Y -registers . You can even perform vector addition and
subtraction using rectangular to polar coordinate conversion
and the
Ell
and
~
keys .
Example: In his converted Swordfish aircraft, grizzled bush
pilot Apeneck Sweeney reads an air speed of 150 knots and a
heading of 045
0
from his instruments . The Swordfish is also
being buffeted by a headwind of 40 knots from a bearing of 025° .
What is the a ctual ground speed and course of the Sword-
fish?
Method: The course and ground speed are equal to the sum
of the instrument vector and the wind vector. The vectors
are converted to rectangular coordinates and summed using
the
Ell
and [[] keys . Their sum is recalled by recalling the values
in storage registers
R4 O:y) and R7 (Ix), and the new
rectan-
gular coordinates are then converted back to polar coordinates