Question

Would appreciate some math help !!

Answer 1

(D).
`(√(2) )/(8)` cis
`(47\pi )/(36)`

Explanation:

cis
`\alpha` × cis
`\beta` = cis (
`\alpha` +
`\beta` )

~~~~~~~

`(√(6) )/(6)` cis
`(5\pi )/(9)` ×
`(√(3) )/(4)` cis
`(3\pi )/(4)` = (
`(√(6) )/(6)` ×
`(√(3) )/(4)` )[cis (
`(5\pi )/(9)` +
`(3\pi )/(4)` )] =
`(√(2) )/(8)` cis
`(47\pi )/(36)`