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IN SUMMARY<br />

Key Idea<br />

• Properties used to evaluate numerical expressions and simplify algebraic<br />

expressions also apply to vector addition and scalar multiplication.<br />

Need to Know<br />

• Commutative Property of Addition:<br />

• Associative Property of Addition: 1a ! a ! <br />

<br />

• Distributive Property of Addition: ,<br />

• Adding 0 ! : a ! 0 ! a !<br />

k1a ! b ! b ! b !<br />

2<br />

b ! c ! <br />

<br />

2 ka ! a ! a !<br />

1b !<br />

kb ! c ! 2<br />

kR<br />

• Associative Law for Scalars: m1na ! 2 <br />

• Distributive Law for Scalars: 1m n2a ! 1mn2a !<br />

ma ! mna !<br />

na !<br />

Exercise 6.4<br />

PART A<br />

1. If * is an operation on a set, S, the element x, such that a * x a, is called<br />

the identity element for the operation *.<br />

a. For the addition of numbers, what is the identity element?<br />

b. For the multiplication of numbers, what is the identity element?<br />

c. For the addition of vectors, what is the identity element?<br />

d. For scalar multiplication, what is the identity element?<br />

2. Illustrate the commutative law for two vectors that are perpendicular.<br />

C<br />

3. Redraw the following three vectors and illustrate the associative law.<br />

a<br />

c<br />

b<br />

4. With the use of a diagram, show that the distributive law, k1a ! b ! 2 ka ! kb !<br />

,<br />

holds where k 6 0, kR.<br />

306<br />

6.4 PROPERTIES OF VECTORS<br />

NEL

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