1.

The principal values of `cos^(-1)(-sin(7pi)/(6))` isA. `(5pi)/(3)`B. `(7pi)/(6)`C. `(pi)/(3)`D. none of these

Answer» We have
`cos^(-1)-sin(7pi)/(6)=cos^(-1)-sin(pi+(pi)/(6))=cos^(-1)sin(pi)/(6)`
`=(pi)/(2)-sin^(-1)sin(pi)/(6)=(pi)/(2)-(pi)/(6)=(pi)/(3)`


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