Chapter 16: Problem 49
Evaluate \(2 \int_{0}^{1} e^{x} \sin x d x\) a) \(1.82\) b) \(1.94\) c) \(2.05\) d) \(2.16\)
Short Answer
Expert verified
Answer: The value of the integral is approximately (b) \(1.94\).
Step by step solution
01
Choose Functions u and dv
Choose the functions \(u\) and \(dv\) as follows:
\(u = e^x\) (since its derivative will simplify to itself)
\(dv = \sin x dx\) (since we know how to integrate the sin function)
02
Find Derivatives and Integrals for u and dv
Differentiate \(u\) with respect to \(x\) and integrate \(dv\) with respect to \(x\)
\(du = e^x dx\)
\(v = -\cos x\)
03
Apply Integration by Parts
Apply the integration by parts formula to the problem
\(\int_{0}^{1} e^x \sin x dx = [e^x (-\cos x)]_{0}^{1} - \int_{0}^{1} -e^x \cos x dx\)
04
Calculate Initial Result
Evaluate the expression:
\([e^x (-\cos x)]_{0}^{1} = (e^1 (-\cos 1)) - (e^0 (-\cos 0))\)
Now we need to calculate the remaining integral \(\int_{0}^{1} -e^x \cos x dx\) by applying integration by parts again.
05
Apply Integration by Parts the Second Time
Choose the functions \(u\) and \(dv\) as follows:
\(u = -e^x\)
\(dv = \cos x dx\)
Differentiate \(u\) with respect to \(x\) and integrate \(dv\) with respect to \(x\):
\(du = -e^x dx\)
\(v = \sin x\)
Apply the integration by parts formula again:
\(\int_{0}^{1} -e^x \cos x dx = [-e^x (\sin x)]_{0}^{1} - \int_{0}^{1} \sin x (-e^x) dx\)
06
Calculate Remaining Terms
Evaluate the expression:
\([-e^x (\sin x)]_{0}^{1} = (-e^1 (\sin 1)) - (-e^0 (\sin 0))\)
Now, we need to find the remaining integral targeted in previous steps.
07
Combine Results
Substitute the calculated values back into the original integral:
\(\int_{0}^{1} e^x \sin x dx = (e^1 (-\cos 1)) - (e^0 (-\cos 0)) - (-e^1 (\sin 1)) + (e^0 (\sin 0)) - \int_{0}^{1} \sin x (-e^x) dx\)
Notice that the expression now involves only the same integral expression that we started with:
\(\int_{0}^{1} e^x \sin x dx = e - 1 + \sin 1 - \int_{0}^{1} e^x \sin x dx\)
08
Solve for the Integral
Rearrange to solve for the integral.
\(\int_{0}^{1} e^x \sin x dx = \frac{e - 1 + \sin 1}{2}\)
Now, multiply the result by 2 as given in the original problem:
\(2\int_{0}^{1} e^x \sin x dx = e - 1 + \sin 1\)
09
Compare to Options
Compare the final result to the given options and choose the correct one.
a) \(1.82\)
b) \(1.94\)
c) \(2.05\)
d) \(2.16\)
Using a calculator, we get:
\(e - 1 + \sin 1 ≈ 1.94\)
Therefore, the correct answer is (b) \(1.94\).
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