Given $\cos t=-\frac{2}{7}$, evaluate the indicated functions. Write your answer as a simplified fraction, if necessary.
Part 1 of 3
(a) $\cos (-t)=-\frac{2}{7}$
Part: $1 / 3$
Part 2 of 3
(b) $\cos (t-2 \pi)=\square$

Answer

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Answer

Final Answer: $ \boxed{-\frac{2}{7}} $

Steps

Step 1 ：Recall that the cosine function is an even function, which means that $ \cos(-t) = \cos(t) $.

Step 2 ：Given that $ \cos(t) = -\frac{2}{7} $, we can conclude that $ \cos(-t) $ should also be $ -\frac{2}{7} $.

Step 3 ：Final Answer: $ \boxed{-\frac{2}{7}} $