Question Detail

MTH 102 MTH 102 Past Questions Objective Question

Question

Evaluate ∫ (e2x + e-2x) / (e2x - e-2x) dx.
Options
A <i>(1/4) ln|e<sup>2x</sup> - e<sup>-2x</sup>| + C</i>
B <i>(1/2) ln|e<sup>2x</sup> + e<sup>-2x</sup>| + C</i>
C <i>(1/2) ln|e<sup>2x</sup> - e<sup>-2x</sup>| + C</i>
Correct Answer
D <i>(1/4) ln|e<sup>2x</sup> + e<sup>-2x</sup>| + C</i>
Correct Answer

Option C is the correct answer.

Detailed Explanation

This integral is of the form ∫ f'(x)/f(x) dx = ln|f(x)| + C.Let the denominator be f(x) = e2x - e-2x.Then, calculate its derivative: f'(x) = d/dx(e2x - e-2x) = 2e2x - (-2)e-2x = 2e2x + 2e-2x = 2(e2x + e-2x).Notice that the numerator of the integrand is (e2x + e-2x), which is exactly (1/2)f'(x).So, we can rewrite the integral as:∫ (1/2) · (2(e2x + e-2x)) / (e2x - e-2x) dx = (1/2) ∫ f'(x)/f(x) dx= (1/2) ln|f(x)| + CSubstitute f(x) back:= (1/2) ln|e2x - e-2x| + C.

Hint

Look for a pattern where the numerator is a multiple of the derivative of the denominator.

Question Info