CCSS Honors 9.2 Example 4

A bicycle wheel has 24 evenly spaced spokes. Use two methods to find the exact value of [math]\cos \theta[/math], where [math]\theta[/math] is the angle between consecutive spokes. For the first method, use the half-angle identity for cosine. For the second, use the angle difference formula for cosine. What do you notice about the two resulting numerical expressions for [math]\cos \theta[/math]?

[list=1] [*]Find [math]\theta[/math], the angle between consecutive spokes. [*]Find the exact value of [math]\cos \theta[/math] by using the half-angle identity for cosine. [*]Find the exact value of [math]\cos \theta[/math] by using the angle difference formula for cosine. [*]Compare the two expressions for [math]\cos \theta[/math]. Use a calculator to verify that the results of the two expressions are equivalent. [/list]