Question

Vector a = 4i + 5j

Vector b = 3i + 6j

Find the dot product.

Answer 1

42

Explanation:

a*b = 4*3 + 5*6 = 12 + 30 ( where i*i = j*j = 1)

∴ a*b = 42

Answer 2

Explanation:

a · b = (4)(3) + (5)(6)

a · b = 12 + 30

a · b = 42