Calculator for finding the Area of a circle
  There are an infinite number of trig formulas
Related Chapters
 that people could think up. 
 Obviously you can't remember them all.
 After you have worked with trig for a while,
 you will find that you have memorized some trig values.
 Whether you wanted to or not.
 Things like:
sin 0° =   0 cos 0° =   1.0
sin 30° =   0.5 cos 30° =   0.866
sin 45° =   0.7071 cos 45° =   0.7071
sin 60° =   0.866 cos 60° =   0.5
sin 90° =   1.0 cos 90° =   0


 But for most other angles you have to use a calculator or look them up in a book.

 But what if you didn't have a calculator or a book? What then eh?

 Well most sane people would say:

 Then go get one!

 Well, many math teachers aren't most sane people. (Did that come out right?)


 Anyway, your math teacher may want you to learn more formulas

 for finding other angles.


 Some of these formulas do have other uses,
 and working with them will make you more comfortable
 working with trig stuff in general.
 But if your teacher puts a bunch of time in on these,
 they are probably pretty close to retirement age.
 OK, with that as a pep talk for this page, here we go.

 Imagine you are a Neanderthal. 

 You get offended by the Geico commercial, walk out of your cave,
 fight off a wooly mammoth,
 and decide you need to know what the sine of 15° is.
 You don't remember it, but you do remember the sine of 30°
 and you also remember a formula for finding the sine of half of an angle
 that you already know the sine for:

 Remember, I said use your imagination.
 Imagine that you know all these formulas
 but $2 trig calculators haven't been invented yet.
 So we know the sine of 30° is 0.5,
 so substitute into the formula and get the answer.
more to come on this topic!
copyright 2008 Bruce Kirkpatrick