# Complex -calcul

• December 24th 2009, 12:11 AM
dhiab
Complex -calcul
Prove that :

$\frac{1}{{\sqrt {3 + 4i} }} + \frac{1}{{\sqrt {3 - 4i} }} = \pm \frac{4}{5}
$
• December 24th 2009, 12:31 AM
mr fantastic
Quote:

Originally Posted by dhiab
Prove that :

$\frac{1}{{\sqrt {3 + 4i} }} + \frac{1}{{\sqrt {3 - 4i} }} = \pm \frac{4}{5}
$

Start by expessing 3 + 4i and 3 - 4i in polar form and then use deMoivres Theorem.
• December 24th 2009, 02:06 AM
Lucio Carvalho
Hello dhiab,
I agree with mr. fantastic, but here it is another way.
I hope you will understand!
Bye!
• December 24th 2009, 06:57 AM
Soroban
Hello, Lucio!

Lovely solution!