From a single section of a single chapter of an actual textbook:
... it can easily be shown that the boundary of the specularity is defined by (see exercises) .
Okay, fair enough.
It is easily shown (see exercises) that the normal to a parametric surface ...
Easy, my ass.
There are two obvious possibilities. We explore the consequences of these models in the exercises.
I obviously knew you were going to say that.
We explore the minimization problem in the exercises.
Are you guys bored writing this chapter?
... (you can convince yourself of this with the aid of a spoon).
The recovered surface does not depend on the choice of curve (exercises).
Okay, now you're just getting lazy.
... (it is complicated, but not difficult, to build more elaborate models).
Complicated, but not difficult... complicated... not difficult... until just now, I thought those two words were the same thing.
By the way, here's a couple of typical exercises:
2.10. Read the book Colour and Light in Nature, by Lynch and Livingstone, published by Cambridge University Press, 1995.
2.12. Make a world of black objects and another of white objects (paper, glue, and spraypaint are useful here) and observe the effects of interreflections.