13.5 – The Cosine Function

I. Writing and Graphing Cosine Functions The cosine function, y = cos θ, matches the x- coordinates of the terminal side as it travels around the unit circle. The cosine function, y = cos θ, matches the x- coordinates of the terminal side as it travels around the unit circle. Using a table, plot the values of y = cos θ, from Using a table, plot the values of y = cos θ, from 0  2π

When graphing the cosine function, all properties remain the same in regards to amplitude, period, and cycles as with the sine function When graphing the cosine function, all properties remain the same in regards to amplitude, period, and cycles as with the sine function

Example 1: graph the following: Example 1: graph the following: A) y= 3 cos θ A) y= 3 cos θ B) f(x) = -1/2 cos 3θ B) f(x) = -1/2 cos 3θ C) g(x) = 2 cos (3π/2) θ C) g(x) = 2 cos (3π/2) θ

II. Solving Trigonometric Equations You can solve trig equations be graphing on the calculator and treating as systems and viewing the intersection points You can solve trig equations be graphing on the calculator and treating as systems and viewing the intersection points

Example 2: Using the calculator, solve the following: Example 2: Using the calculator, solve the following: A) cos 2θ = ½ A) cos 2θ = ½ B) -2 cos π/3 θ =.3 B) -2 cos π/3 θ =.3