There's really no such thing as the value of a triangle.
Every triangle has three sides, three angles, a base, a height, and an area,
and there could be problems that ask us to find any one of those.
Whatever we need to find, the process is always the same:
-- Take the information that's given.
-- Gather up everything you can remember that talks about a relationship
between what you're given and what you need to find.
-- Use them together to find the missing value.
