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निम्नलिखित व्यंजकों के मान ज्ञात कीजिए - `cos^(-1)(cos.(13pi)/(6))`

Answer» चूँकि `cos^(-1)` की मुख्य शाखा का परिसर `[0,pi]` होता है।
`therefore" "cos^(-1)(cos.(13pi)/(6))ne(13pi)/(6)," "[because(13pi)/(6) cancel in [0,pi]]`
अब, `cos^(-1)(cos.(13pi)/(6))`
`=cos^(-1)[cos(2pi+(pi)/(6))]," "[because(13pi)/(6)=2pi+(pi)/(6)]`
`=cos^(-1)(cos.(pi)/(6))," "[because cos(2pi+theta)=cos theta]`
`=(pi)/(6)in [0,pi]," "[because cos^(-1)(cos theta)=theta]`
`therefore cos^(-1)(cos.(13pi)/(6))=(pi)/(6).`


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