Question

How do you multiply `(2+i)(2-3i)` in trigonometric form?

Answer 1

`7-4i`

Explanation:

First, we have to know that
`i^1=i`
`i^2=-1`
`i^3=-i`
`i^4=1`

Then, we can expend the expression and simplify it with the above rule:

`(2+i)(2-3i)`
`=4-6i+2i-3i^2`
`=4-4i-3i^2`
`=4-4i-3(-1)`
`=4-4i+3`
`=7-4i`

It's the answer! Hope it can help you :)