Here are postal rates as a piecewise function:
Some of the piecewise functions in the text have semi-circles. The equation of a circle is x^2 + y^2 = r^2, where r is the radius. Circles can be translated like any other relation.
If you solve for 'y', you obtain the equation of the semi-circle (each of which is a function).
A better picture of each half of the circle from above.
Assignment from this sections is p70 #1-5.
Function characteristics are even, odd, increasing, decreasing, one-to-one, many-to-one.
Notes from this are located here.






