Homework Help: Find the argument

1. Oct 7, 2012

utkarshakash

1. The problem statement, all variables and given/known data
$arg \left\{ sin \frac{8∏}{5} + i \left( 1 + cos\frac{8∏}{5}\right) \right\}$

2. Relevant equations

3. The attempt at a solution
$2sin \frac{4∏}{5} cos \frac{4∏}{5} + i2cos^{2} \frac{4∏}{5} \left(cos2θ=2cos^{2}θ-1 and sin2θ=2sinθcosθ\right)$

After simplification what is the next step?

2. Oct 9, 2012

HallsofIvy

Do you know what "argument" means in this problem?