Spoken Tutorial, IIT Bombay 
https://spoken-tutorial.org
LaTeX 
Feedback Diagram with Maths - Assignments ------------------------------------------------------------------------------------------------------------------------

(a) Make the diagram created in this tutorial more symmetric and beautiful

(b) Try out different mathematical expressions

(c) Try out other options, such as flip and rotate, not covered in the spoken tutorial

(d) Try to build different diagrams

(e) Explore the library

(f) Do an internet search and locate information relevant to Xfig