Question

on
1. If a=6i+2j+3k and b = 2i-9j +6k, then
find a.b and the angle between ā and b.​

Answer 1

Step-by-step explanation:

2i-6i+(-9j)-2j+6k-3k

-4i-11j+3k

Answer 2

Answer:

a . b= 12

angle between a and b ie. (a , b) = cos^-1( $\frac{12}{77}$ )

Step-by-step explanation:

a . b = (6i+2j+3k) . (2i-9j+6k)

        = (6*2)+(2*-9)+(3*6)

        = 12-18+18

        =12

|a| = | 6i+2j+3k | = $\sqrt{36+4+9}$ = 7

|b| = | 2i-9j+6k | = $\sqrt{4+81+36\\\\}$ = 11

cos (a , b) = $\frac{a . b}{| a | | b |}$

                 = $\frac{12}{7*11}$

                 = $\frac{12}{77}$

angle between a and b ie. (a , b) = cos^-1( $\frac{12}{77}$ )