Question Detail

MTH 102 MTH 102 Past Questions Objective Question

Question

Differentiate the implicit functions x2 sin y - e2y cos x = 3x2 + 2x - 5 with respect to x.
Options
A dy/dx = (6x - 2xsiny - sinxe<sup>2y</sup> + 2) / (x<sup>2</sup>cosy + 2cosxe<sup>2y</sup>)
B dy/dx = (6x + 2xsiny - sinxe<sup>2y</sup> + 2) / (x<sup>2</sup>cosy - 2cosxe<sup>2y</sup>)
C dy/dx = (6x - 2xsiny - sinxe<sup>2y</sup> + 2) / (x<sup>2</sup>cosy - 2cosxe<sup>2y</sup>)
Correct Answer
D dy/dx = (-6x - 2xsiny - sinxe<sup>2y</sup> - 2) / (x<sup>2</sup>cosy - 2cosxe<sup>2y</sup>)
Correct Answer

Option C is the correct answer.

Detailed Explanation

Differentiate each term of x2 sin y - e2y cos x = 3x2 + 2x - 5 with respect to x using the product rule and chain rule where necessary.1. d/dx(x2 sin y): (2x)sin y + x2(cos y dy/dx) = 2x sin y + x2 cos y dy/dx2. d/dx(-e2y cos x): -[(d/dx(e2y))cos x + e2y(d/dx(cos x))] = -[(2e2y dy/dx)cos x + e2y(-sin x)] = -2e2y cos x dy/dx + e2y sin x3. d/dx(3x2 + 2x - 5): 6x + 2Combine the derivatives:2x sin y + x2 cos y dy/dx - 2e2y cos x dy/dx + e2y sin x = 6x + 2Group terms with dy/dx:(x2 cos y - 2e2y cos x) dy/dx = 6x + 2 - 2x sin y - e2y sin xSolve for dy/dx:dy/dx = (6x - 2x sin y - e2y sin x + 2) / (x2 cos y - 2e2y cos x).Note that sin x e2y is the same as e2y sin x.

Hint

Apply implicit differentiation. Remember to use the product rule for terms with both x and y, and the chain rule for derivatives of y with respect to x.

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