Same chapter3 marksDifficulty: Medium
Prove that (sec A − tan A)(sec A + tan A) = 1.
Trigonometric Identities
4 marksDifficulty: Hard
Prove that (1 + sin A)/(1 − sin A) = (sec A + tan A)2.
Original Khojo Papers practice question — not from a past board paper.
Answer
Multiplying numerator and denominator by (1 + sin A) gives (1 + sin A)2/cos2A, which is (1/cos A + sin A/cos A)2 = (sec A + tan A)2.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
The step that matters is 1 − sin2A = cos2A in the denominator.
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