Figure 4. Illustration of Lighted Area and Shadow Area of a Polygonal Domain

From

The Wave Equation with Dynamic Wentzell Boundary Condition in Polygonal and Polyhedral Domains: Observation and Exact Controllability

Tawfik Masrour

International Journal of Partial Differential Equations and Applications. 2014, 2(1), 13-22 doi:10.12691/ijpdea-2-1-3