integral of 1/(sqrt(1+3x+x^2))

Lösung

\int \frac{1}{1 + 3 x + x ^{2}} d x

ln \frac{1}{5} (4 x^{2} + 12 x + 4) + \frac{2}{5} x + \frac{3}{5} + C

Schritte zur Lösung

\int \frac{1}{1 + 3 x + x ^{2}} d x

Vervollständige das Quadrat

1 + 3 x + x^{2} : (x + \frac{3}{2})^{2} - \frac{5}{4}

= \int \frac{1}{( x + \frac{3}{2} ) ^{2} - \frac{5}{4}} d x

Wende U-Substitution an

= \int \frac{2}{4 u ^{2} - 5} d u

Entferne die Konstante:

\int a \cdot f (x) d x = a \cdot \int f (x) d x

= 2 \cdot \int \frac{1}{4 u ^{2} - 5} d u

Trigonometrische Substitution anwenden

= 2 \cdot \int \frac{sec ( v )}{2} d v

Entferne die Konstante:

\int a \cdot f (x) d x = a \cdot \int f (x) d x

= 2 \cdot \frac{1}{2} \cdot \int sec (v) d v

Nutze das gemeinsame Integral :

\int sec (v) d v = ln ∣ tan (v) + sec (v) ∣

= 2 \cdot \frac{1}{2} ln ∣ tan (v) + sec (v) ∣

Ersetze zurück

= 2 \cdot \frac{1}{2} ln tan (arcsec (\frac{2}{5} (x + \frac{3}{2}))) + sec (arcsec (\frac{2}{5} (x + \frac{3}{2})))

Vereinfache

2 \cdot \frac{1}{2} ln tan (arcsec (\frac{2}{5} (x + \frac{3}{2}))) + sec (arcsec (\frac{2}{5} (x + \frac{3}{2}))) : ln \frac{1}{5} (4 x^{2} + 12 x + 4) + \frac{2}{5} x + \frac{3}{5}

= ln \frac{1}{5} (4 x^{2} + 12 x + 4) + \frac{2}{5} x + \frac{3}{5}

Füge eine Konstante zur Lösung hinzu

= ln \frac{1}{5} (4 x^{2} + 12 x + 4) + \frac{2}{5} x + \frac{3}{5} + C

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