Q21 of 48 Page 84

Prove the following with the help of identities:

(sin A + cosec A)2 + (cos A + sec A)2 = 7 + tan2A + cot2A

Taking L.H.S we get,


(sin A + cosec A)2 + (cos A + sec A)2 = 7 + tan2 A + cot2 A


Expanding the terms using: (a + b)2 = a2 + b2 + 2.a.b


sin2 A + cosec2 A + 2.sin A.cosec A + cos2 A + sec2 A + 2.sec A.cos A


(sin2 A + cos2 A) + 2.sin A. + cosec2 A + sec2 A + 2.cos A.


1 + 2 + cosec2 A + sec2 A + 2


5 + (1 + cot2 A) + (1 + tan2 A)


5 + 1 + 1 + tan2 A + cot2 A


7 + tan2 A + cot2 A


= R.H.S


Hence, proved.


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