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Write the principal value of, `cos^(-1) (cos(7pi)/6)` |
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Answer» Here, we will use `cos(pi+x) = cos(pi-x)` `:. cos((7pi)/6) = cos(pi+pi/6) = cos(pi-pi/6)` `= cos((5pi)/6)` `:. cos^-1(cos((7pi)/6)) = cos^-1(cos((5pi)/6))` `=(5pi)/6`, which is the required principal value as it is between `0` and `pi`. |
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