While you were exploring you may have noticed that the function starts as a horizontal line along the x-axis. If you only change the value of [math]a\,[/math] the line remains horizontal and moves up and down with the value of [math]a\,[/math]. If the value of [math]b\,[/math] is changed from zero the line moves back and forth across the x-axis. We like to say it oscillates! If the value of [math]c\,[/math] is changed from zero (when [math]a\,[/math] and [math]b\,[/math] are not zero) the crests and troughs moves side to side sometimes crossing the y-axis.

- What parameter best describes the amplitude of the wave?
- [math]a\,[/math]
- Absolutely correct! The value of [math]a\,[/math] determines how high the crests are and how low the troughs are.

- [math]b\,[/math]
- Incorrect, the value of [math]b\,[/math] determines how quickly the sinusoidal wave oscillates.

- [math]c\,[/math]
- Incorrect, [math]c\,[/math] is often described as the phase shift because the wave looks the same except for a shift to the right or left.

- [math]d\,[/math]
- Incorrect, there is no [math]d\,[/math] in the equations [math]f(x)\,[/math]

**Tip:** You might want to have a look at the definition of

amplitude