D={(r,θ)∣3≤r≤5,π4≤θ≤π2}D = \bigg\lbrace (r, \theta)|3 \le r \le 5, \frac{\pi}{4} \le \theta \le \frac{\pi}{2}\bigg\rbraceD={(r,θ)∣3≤r≤5,4π≤θ≤2π}