Factorize z 6 </msup> + 1 , and deduce cos &#x2061;<!-- ⁡ --> <mr

indimiamimactjcf

indimiamimactjcf

Answered question

2022-05-12

Factorize z 6 + 1, and deduce cos 3 x = cos x ( 2 cos x + 3 ) ( 2 cos x 3 )

Answer & Explanation

Mackenzie Zimmerman

Mackenzie Zimmerman

Beginner2022-05-13Added 15 answers

z 6 + 1
= ( z 2 + 1 ) ( z 2 + 3 z + 1 ) ( z 2 3 z + 1 )
= ( z 4 + z 2 ) ( z + 3 + 1 / z ) ( z 3 + 1 / z )
Divide by z 3 :
z 3 + z 3 = ( z + 1 / z ) ( z + 3 + 1 / z ) ( z 3 + 1 / z )
Let z = e i x , then z + 1 / z = 2 cos x and z 3 + z 3 = 2 cos 3 x
2 cos 3 x = 2 cos x ( 2 cos x + 3 ) ( 2 cos x 3 )
cos 3 x = cos x ( 2 cos x + 3 ) ( 2 cos x 3 )

Do you have a similar question?

Recalculate according to your conditions!

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?