D={(r,θ)∣0≤r≤tanθsecθ,0≤θ≤π4}D = \bigg\lbrace (r, \theta)|0 \le r \le tan\theta sec\theta, 0 \le \theta \le \frac{\pi}{4}\bigg\rbraceD={(r,θ)∣0≤r≤tanθsecθ,0≤θ≤4π}