In radians, pi is equal to 180º
Then, for each pi, we add 180º. we know that sin(pi) = 0 and cos(pi) = -1
Then:
but, we can see that 180º + 180º = 360º = 0º
Then, all we need to know is the value of the trigonometric functions at pi (in this case, it's the same 7pi or -7pi)
Thus:
![\begin{gathered} \cos (\pi)=-1 \\ \sin (\pi)=0 \\ \tan (\pi)=(\sin(\pi))/(\cos(\pi))=(0)/(-1)=0 \\ \cot (\pi)=(1)/(\tan(\pi))=(\cos (\pi))/(\sin (\pi))=(-1)/(0)=\text{undefined} \\ \sec (\pi)=(1)/(\cos (\pi))=(1)/(-1)=-1 \\ \csc (\pi)=(1)/(\sin(\pi))=(1)/(0)=\text{ undefined} \\ \\ \end{gathered}]()