How to use special right triangles to evaluate for cosine of 45 degrees

The video tutorial explains the properties of special right triangles, specifically the 45-45-90 triangle. It demonstrates how to calculate the cosine of 45 degrees using these properties, simplifying the expression, and rationalizing the denominator. The tutorial also shows how to verify the result using a calculator, comparing the fraction and decimal forms of the cosine value.

Explain how to rationalize the denominator when calculating cosine.

What is the decimal value of the cosine of 45 degrees?