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Prove that Tan 2 a Tan 2 a − 1 + Cos E C 2 a Sec 2 a − Cos E C 2 a = 1 1 − 2 C O 2 a - Mathematics

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प्रश्न

Prove that `(tan^2"A")/(tan^2 "A"-1) + (cosec^2"A")/(sec^2"A"-cosec^2"A") = (1)/(1-2 co^2 "A")`

योग

उत्तर

Taking L.H.S.

`(tan^2"A")/(tan^2 "A"-1) + (cosec^2"A")/(sec^2"A"-cosec^2"A")`


`((sin^2"A")/(cos^2"A"))/((sin^2"A")/(cos^2"A")-1)+ ((1)/(sin^2"A"))/((1)/(cos^2"A")-(1)/(sin^2"A"))  ...(∵ tan "A" = (sin"A")/(cos"A"))`

 

= `(sin^2"A")/(sin^2 "A"- cos^2"A") + (1)/(sin^2 "A"). (sin^2"A" cos^2"A")/(sin^2"A"-cos^2"A")`


= `(sin^2"A")/(sin^2 "A"- cos^2"A") + (cos^2"A")/(sin^2 "A"- cos^2"A")`


= `(sin^2 "A"+ cos^2"A")/(sin^2"A"-cos^2"A")`


= `(1)/(1-cos^2"A"-cos^2"A")   ...(∵ sin^2 "A" = 1 -cos^2"A")`


= `(1)/(1-2 cos^2 "A")`


= R.H.S.

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2018-2019 (March) Delhi Set 2

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