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2. Yes, cos is an even function so cos(-x) = cos(x). So instead of that sign swapping from plus to minus on the RHS, it would stay plus, but the minus sign from inside the brackets would go, i.e:

a + cos(-pi b) = a + cos(pi b).

Yes, as tan is also an odd function, that equality would also hold for tan.
3. (Original post by claret_n_blue)
Yes, cos is an even function so cos(-x) = cos(x). So instead of that sign swapping from plus to minus on the RHS, it would stay plus, but the minus sign from inside the brackets would go, i.e:

a + cos(-pi b) = a + cos(pi b).

Yes, as tan is also an odd function, that equality would also hold for tan.
Hey thanks I understand it better now- you explained that really well !

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