integral of xe^{-inpix}

Lösung

\int x e^{- inπ x} d x

\frac{1}{π ^{2} n ^{2}} (cos (πn x) + πn x sin (πn x)) + i \frac{1}{π ^{2} n ^{2}} (- sin (πn x) + πn x cos (πn x)) + C

Schritte zur Lösung

\int x e^{- inπ x} d x

Vereinfache

x e^{- inπ x} : x cos (πn x) - i x sin (πn x)

= \int x cos (πn x) - i x sin (πn x) d x

Wende die Summenregel an:

\int f (x) \pm g (x) d x = \int f (x) d x \pm \int g (x) d x

= \int x cos (πn x) d x - \int i x sin (πn x) d x

\int x cos (πn x) d x = \frac{1}{π ^{2} n ^{2}} (πn x sin (πn x) + cos (πn x))

\int i x sin (πn x) d x = i \frac{1}{π ^{2} n ^{2}} (sin (πn x) - πn x cos (πn x))

= \frac{1}{π ^{2} n ^{2}} (πn x sin (πn x) + cos (πn x)) - i \frac{1}{π ^{2} n ^{2}} (sin (πn x) - πn x cos (πn x))

Vereinfache

\frac{1}{π ^{2} n ^{2}} (πn x sin (πn x) + cos (πn x)) - i \frac{1}{π ^{2} n ^{2}} (sin (πn x) - πn x cos (πn x)) : \frac{1}{π ^{2} n ^{2}} (cos (πn x) + πn x sin (πn x)) + i \frac{1}{π ^{2} n ^{2}} (- sin (πn x) + πn x cos (πn x))

= \frac{1}{π ^{2} n ^{2}} (cos (πn x) + πn x sin (πn x)) + i \frac{1}{π ^{2} n ^{2}} (- sin (πn x) + πn x cos (πn x))

Füge eine Konstante zur Lösung hinzu

= \frac{1}{π ^{2} n ^{2}} (cos (πn x) + πn x sin (πn x)) + i \frac{1}{π ^{2} n ^{2}} (- sin (πn x) + πn x cos (πn x)) + C

\int \frac{1}{1 + 8 x} d x

\int sec^{4} (a) x d x

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\int (3 x^{3} + 4 x - 7) d x

\int x + 2 x d x