Write the Word or Phrase That Best Completes Each Statement

Short Answer

Write the word or phrase that best completes each statement or answers the question.
- $$\text { If } f ( \theta ) = \sin \theta \text { and } f ( a ) = - \frac { 1 } { 9 } , \text { find the exact value of } f ( a ) + f ( a - 4 \pi ) + f ( a - 2 \pi )$$