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The principal value of `cos^(-1)(-1/2)` isA. `-pi/3`B. `(2pi)/3`C. (4pi)/3`D. `pi/3`

Answer» Correct Answer - B
Let `cos^(-1)(-1/2)=x`, where `x in [0,pi]`.
Then, `cosx=-1/2=-cospi/3 = cos(pi-pi/3)=cos(2pi)/3 rArr x=(2pi)/3`.


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