Answer
True.
Work Step by Step
We know that $\sin$, $\csc$, $\tan$, $\cot$ are odd functions, which means $f(-\theta)=-f(\theta).$
We also know that $\cos$, $\sec$, are even functions, which means $f(-\theta)=f(\theta).$
There are no trigonometric functions left, hence the statement is true.
