If y = tan⁻¹((a cos x − b sin x)/(b cos x + a sin x)), then dy/dx is:
If y = tan⁻¹((a cos x − b sin x)/(b cos x + a sin x)), then dy/dx is:
- A. −1
- B. 1
- C. 0
- D. −2
Answer: A) −1
Explanation: Put a = r cos α, b = r sin α. Then expression = tan⁻¹((r cos(α+x))/(r sin(α+x))) = tan⁻¹(cot(α+x)) = π/2 − (α+x). So y′ = −1.
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