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Railways PYQCBT 1 2020

RRB NTPC · Question 81

If x = a sin t, y = b tan t, then \(\rm \frac{a^2}{x^2} - \frac{b^2}{y^2}\) is:

  1. 0

  2. 1

  3. -1

  4. 2

Show answer & explanation

Answer: (B) 1

Explanation

a/x = 1/sin t = cosec t and b/y = 1/tan t = cot t. So a²/x² − b²/y² = cosec²t − cot²t = 1.