HP 39G Master Guide

175
The dot product
Eg. 4 Find the angle between the vectors (3,4)a
=
and (4,1)b
=
.
Using the formula that
..cosab ab
θ
•=
where ab
•
is the dot product, we can
rearrange to obtain:
cos
.
ab
ab
θ
•
=
Therefore:
2222
(3,4) (4,1)
cos
(3,4) . (4,1)
3441
34.41
16
517
39 09
θ
θ
•
=
×+×
=
+
+
=
=⋅
"
On the calculator, the functions DOT and ABS
give the dot product and magnitude
respectively, when fed with vectors. The
hp 39g+ writes vectors as row matrices. For
example (3,4)a = would be written as [3,4].
The calculations are shown in the two screen
shots on the right. Remember to change into
degree mode first.
The list of matrix functions available through the MATH menu is covered
starting on page 271. Not all functions are covered, since many of them go
far beyond the requirements of the average student at whom this book is
aimed.
1 2 3 4 5-1-2-3-4-5
1
2
3
4
5
-1
-2
-3
-4
-5
θ
(3,4)
(4,1)

HP 39G Specifications

General

Brand	HP
Model	39G
Category	Calculator
Language	English