Module 4: Foundations of Trigonometry

 

tip

When sketching a graph, be sure to remember these steps:

  • Label your axes.
  • Show a scale on both the x- and y-axes.
  • Plot some points, and then use those points to sketch a smooth curve.
  • Try to fill up most of the space available.
  • Show at least one full cycle.


Self-Check 1
  1. Determine the amplitude of the following graph. Answer

     
    This graph is sinusoidal with a maximum of 3 and a minimum of minus 3.  It takes three cycles of the graph to go from negative pi to 2 pi.
  2. Draw a cosine graph with an amplitude of 5. Answer

This photo shows a student graphing a trigonometric function.

iStockphoto/Thinkstock

In Try This 2 you looked at the general shape of a cosine function and focused on some of the cosine’s vertical characteristics. You will next look at some of the horizontal characteristics of the graphs of sine and cosine functions.


Try This 3
  1. Use Unit Circle to Graph to plot the sine and cosine function.

     
    This is a play button that opens Unit Circle to Graph.
  2. How do your graphs from Try This 1 and Try This 2 compare to these graphs?
  3. Turn on only the sine function. As the value of θ increases, the graph begins to repeat itself in a regular manner. A function that repeats itself in this way is called a periodic function. The period of a function is the horizontal length of one cycle on a periodic graph. What is the period of the graph y = sin θ in radians and degrees?

     
    This illustration shows a sinusoidal curve. A horizontal line between two peaks labels one period.  A second horizontal line between adjacent corresponding points of the curve also labels one period.
  4. What are the θ-intercepts, or zeros, of y = sin θ?
  5. What is the period of the graph y = cos θ in radians and degrees?
  6. What are the θ-intercepts, or zeros, of y = cos θ?

course folder Save your responses in your course folder.