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

Jan 27, 2018

$\left(8 - 7 i\right) \left(6 - 4 i\right) = 20 - 74 i$

#### Explanation:

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

$\left(8 - 7 i\right) \left(6 - 4 i\right) = 8 \left(6 - 4 i\right) - 7 i \left(6 - 4 i\right)$
$\text{ } = 48 - 32 i - 42 i + 28 {i}^{2}$
$\text{ } = 48 - 74 i - 28$
$\text{ } = 20 - 74 i$