Pre-Cal

Evaluate the following. Show you work:

A). tan^-1(tan(5π/6))

B). cos^-1(cos(-π/4))

Can someone please show me the steps to evaluating this problem. I've been working this for 2 hours today and all of last night, I still can't seem to figure it out. Please leave notes if possible.

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  1. each inverse trig function has a principal domain. Review those.

    tan 5π/6 = -tan π/6 = -1/√3
    but, tan^-1(-1/√3) = -π/6

    cos -π/4 = cos π/4 = 1/√2
    but, cos^-1(1/√2) = π/4

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  2. Thank you.

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