Wolfram Research
Wolfram Math World: Inverse Cosine
A site that deals with inverse cosine. Article includes the definition, formulas including the Maclaurin series for the inverse cosine function, and examples, as well as numerous links to related terms.
Lawrence Hall of Science
The Math Page: Trigonometry: Inverse Trigonometric Function
Here is a site that clearly and thoroughly explains each of the six inverse trigonometric functions. There are example problems solved, problems for the student to attempt, and answers to the student problems. Point this site out to...
Interactive Mathematics
Interactive Mathematics: Values of Trigonometric Functions
How do you determine the value f a trig function? Find the answer here. This tutorial shows how to find trig values from 45-45-90 and 30-60-90 triangles, as well as how to use the calculator to find both trig values and angle measures.