Another one! I'm really sorry. This time I'm not sure where I went wrong.

Express in polar form, (1/(sqrt(21) - sqrt(7)i)*)

Conjugate, so I got (1/(sqrt(21) + sqrt(7)i))

Let z = sqrt(21) + sqrt(7)i

In modulus argument form ie. cis form, I got sqrt(30)cis(pi/6)

For the modulus of (1/(sqrt(21) - sqrt(7)i)*),

I got 1/sqrt(30)

But the answer is (sqrt(7)/14)!

Thank you very much for your time,

J.