Question Detail

MTH 102 MTH 102 Past Questions Objective Question

Question

Find dy/dx if y = cos(5x-3y).
Options
A <code>-5sin(5x-3y) / (1-3sin(5x-3y))</code>
B <code>-5sin(5x-3y) / (1+3sin(5x-3y))</code>
Correct Answer
C <code>5sin(5x-3y) / (1-3sin(5x-3y))</code>
D <code>5sin(5x-3y) / (1+3sin(5x-3y))</code>
Correct Answer

Option B is the correct answer.

Detailed Explanation

To find dy/dx for y = cos(5x-3y), we use implicit differentiation and the chain rule:
  1. Differentiate both sides with respect to x:dy/dx = -sin(5x-3y) * d/dx(5x-3y)
  2. Apply the chain rule to d/dx(5x-3y):d/dx(5x-3y) = 5 - 3 dy/dx
  3. Substitute this back into the equation:dy/dx = -sin(5x-3y) * (5 - 3 dy/dx)dy/dx = -5sin(5x-3y) + 3sin(5x-3y) dy/dx
  4. Rearrange the terms to group dy/dx on one side:dy/dx - 3sin(5x-3y) dy/dx = -5sin(5x-3y)dy/dx (1 - 3sin(5x-3y)) = -5sin(5x-3y)
  5. Solve for dy/dx:dy/dx = -5sin(5x-3y) / (1 - 3sin(5x-3y))
This matches option B.

Hint

Remember to use implicit differentiation and the chain rule. Gather all dy/dx terms on one side.

Question Info