Question

Find a.b when a = i + 2j – 3k, b = i + 2j – 3k, b= i+2j-k

Select one:

5

2

8

3

Answer 1

Correct option is (c) 8

Given, \(\vec a = \hat i + 2\hat j-3\hat k\)

and \(b = \hat i + 2\hat j - \hat k\)

So scalar product

\(\vec a. \vec b = (\hat i + 2\hat j- 3\hat k)(\hat i + 2\hat j - \hat k)\)

\(= 1(1) +4(1)+ 3(1)\)

\(= 1 + 4 + 3\)

\(= 8\)