Domain Roots of ${g}_{1}\left(u\right)$ Roots of ${g}_{2}\left(v\right)$ Accessible region ${A}_{ℝ}$ 1 0 ${v}_{1}<0<{v}_{2}$ $\varnothing ×\left[{v}_{1},{v}_{2}\right]$ ∅ 2 ${u}_{1}<{u}_{2}<0<{u}_{3}<{u}_{4}$ ${v}_{1}<0<{v}_{2}$ $\left[{u}_{1},{u}_{2}\right]\cup \left[{u}_{3},{u}_{4}\right]×\left[{v}_{1},{v}_{2}\right]$ 2T 3 ${u}_{1}<{u}_{2}<0<{u}_{3}<{u}_{4}$ ${v}_{1}<0<{v}_{2}$ $\left[{u}_{1},{u}_{2}\right]\cup \left[{u}_{3},{u}_{4}\right]×\left[{v}_{1},{v}_{2}\right]$ 2T 4 ${u}_{1}<0<{u}_{2}$ ${v}_{1}<0<{v}_{2}$ $\left[{u}_{1},{u}_{2}\right]×\left[{v}_{1},{v}_{2}\right]$ T 5 ${u}_{1}<0<{u}_{2}$ ${v}_{1}<0<{v}_{2}$ $\left[{u}_{1},{u}_{2}\right]×\left[{v}_{1},{v}_{2}\right]$ T 6 ${u}_{1}<0<{u}_{2}$ ${v}_{1}<0<{v}_{2}$ $\left[{u}_{1},{u}_{2}\right]×\left[{v}_{1},{v}_{2}\right]$ T 7 ${u}_{1}<0<{u}_{2}$ ${v}_{1}<0<{v}_{2}$ $\left[{u}_{1},{u}_{2}\right]×\left[{v}_{1},{v}_{2}\right]$ T 8 ${u}_{1}<0<{u}_{2}$ ${v}_{1}<{v}_{2}<0<{v}_{3}<{v}_{4}$ $\left[{u}_{1},{u}_{2}\right]×\left[{v}_{1},{v}_{2}\right]\cup \left[{v}_{3},{v}_{4}\right]$ 2T 9 ${u}_{1}<0<{u}_{2}$ ${v}_{1}<{v}_{2}<0<{v}_{3}<{v}_{4}$ $\left[{u}_{1},{u}_{2}\right]×\left[{v}_{1},{v}_{2}\right]\cup \left[{v}_{3},{v}_{4}\right]$ 2T 10 ${u}_{1}<0<{u}_{2}$ 0 $\left[{u}_{1},{u}_{2}\right]×\varnothing$ ∅