How to calculate apparent power?

For my exam I need to calculate the apparent power, active power and reactive power.

I know I get the active power from the real part and reactive power from imaginary part of the apparent power. However, I can't find any formulas for my specific problem.

I have

$ U = 82.58 e^{j31.89°} $ and $ I = 1.65 e^{j31.89°} $

The formula I found is

$ S = \frac{1}{2} UI^* $

But it starts with the problem that I don't know how to get from for example $68e^{j30°}$ to something like $68.19 - j42.45$

Used Euler. But know I don't get the correct solution.
I have $S= 0.5* 82.58 e^{j31.89°} 1.65 e^{j31.89°}$
That would be $S=68.13cos(63.78)+j68.13sin(63.78)$

Tried to conjugate "I" like that: $I=1.65 e^{-j31.89°}$
But then $\Phi = 0$

But the solution is $S=68.19 - j42.45$

Answer

Use these identities :-

$z = R.e^{j\theta}$
$Re(z) = R\cos(\theta) = a$
$Im(z) = R\sin(\theta) = b$
$z = a + jb$
$R = |z| = \sqrt{a^2 + b^2}$
$\theta = Arg(z) = \arctan(\frac{b}{a})$

For example:
$56.e^{j40} = 56\cos(40) + 56j\sin(40) = 42.9 + 36.0j$
$75 - j22 = \sqrt{75^2 + 22^2}.e^\arctan(\frac{-22}{75}) = 78.16.e^{-16.3j}$