Complex no: Where did I go wrong

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.

Re: Complex no: Where did I go wrong

Quote:

Originally Posted by

**Tutu** 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.

In order to convert to the polar form, the complex number first needs to be in Cartesian form.

Now that it's in form, try converting to polars.

Re: Complex no: Where did I go wrong