Why does this
-z(L+x) \; , & x\in \left[-L,-z\right]\\ (L-z)x \; , & x\in \left[-z,z\right]\\ z(L-x) \; , & x\in \left[z,L\right] \end{cases}$$ define a $2L$-periodic ...
Angle relations in triangle – math.stackexchange.com
X3nius
Why does this
-z(L+x) \; , & x\in \left[-L,-z\right]\\ (L-z)x \; , & x\in \left[-z,z\right]\\ z(L-x) \; , & x\in \left[z,L\right] \end{cases}$$ define a $2L$-periodic ...