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.

What is the length of the hypotenuse in a 45-45-90 triangle if each leg is of length X?

• X

• 2X

• X * sqrt 2

• X / 2

In a 45-45-90 triangle, what is the cosine of a 45-degree angle?

• X / X

• sqrt 2 / 2

• 1

• 1 / sqrt 2

How do you rationalize the denominator of 1 / sqrt 2?

• Add sqrt 2

• Multiply by sqrt 2 / sqrt 2

• Divide by sqrt 2

• Multiply by 2

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

• 0.5

• 0.866

• 1.414

• 0.707

Which method is NOT used to find the cosine of 45 degrees?

• Rationalizing the denominator

• Using a protractor

• Using a 45-45-90 triangle

• Using a calculator