Question

How do you multiply `(8-7i)(6-4i)` in trigonometric form?

Answer 1

`(8-7i)(6-4i) = 20-74i`

Explanation:

Whilst we could convert each complex number into trigonometric forms, it would be cumbersome to do so, instead we just expand the expression:

`(8-7i)(6-4i) = 8(6-4i) -7i(6-4i)`
`" " = 48-32i - 42i+28i^2`
`" " = 48-74i -28`
`" " = 20-74i`