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| 1. |
Prove that (1 + tan A – sec A) × (1 + tan A + sec A) = 2 tan A |
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Answer» LHS = (1 + tan A – sec A) × (1 + tan A + sec A) (x – y) (x + y) = x2 – y2 here x = 1 + tan A y = sec A LHS = (1 + tan A)2 – (sec A)2 = 1 + tan2 A + 2 tan A – sec2 A = sec2 A + 2 tan A – sec2 A (1 + tan2 A = sec2 A) = 2 tan A = RHS Hence, proved. |
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