1.

`cos[sin^(-1)""(3)/(5)+sin^(-1)""(5)/(13)]` का मान ज्ञात कीजिए ।

Answer» माना `sin^(-1)""(3)/(5)=A` तथा `sin^(-1)""(5)/(13)=B`
` implies sinA=(3)/(5),sinB=(5)/(13)`
`implies cos A=(4)/(5), cosB=(12)/(13)`
अब `cos[A+B]=cosA cos B- sinA sinB`
`=(4)/(5)xx(12)/(13)-(3)/(5)xx(5)/(13)=(48)/(65)-(15)/(65)=(33)/(65)`


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