integral of (sec(x))^3

解

\int (sec (x))^{3} d x

- x sec^{3} (x) cos^{3} (x) + x + \frac{1}{2} sec (x) tan (x) + \frac{1}{2} ln ∣ tan (x) + sec (x) ∣ + C

解答ステップ

\int (sec (x))^{3} d x

三角関数の公式を使用して書き換える

= \int \frac{1}{cos ^{3} ( x )} d x

\frac{1}{cos ^{3} ( x )} = sec^{3} (x) (1 - cos^{3} (x)) + 1

= \int sec^{3} (x) (1 - cos^{3} (x)) + 1 d x

三角関数の公式を使用して書き換える

= \int \frac{1 - cos ^{3} ( x )}{cos ^{3} ( x )} + 1 d x

部分積分を適用する

= x (sec^{3} (x) (1 - cos^{3} (x)) + 1) - \int 3 x sec^{4} (x) sin (x) d x

\int 3 x sec^{4} (x) sin (x) d x = x sec^{3} (x) - \frac{1}{2} sec (x) tan (x) - \frac{1}{2} ln ∣ tan (x) + sec (x) ∣

= x (sec^{3} (x) (1 - cos^{3} (x)) + 1) - (x sec^{3} (x) - \frac{1}{2} sec (x) tan (x) - \frac{1}{2} ln ∣ tan (x) + sec (x) ∣)

簡素化

x (sec^{3} (x) (1 - cos^{3} (x)) + 1) - (x sec^{3} (x) - \frac{1}{2} sec (x) tan (x) - \frac{1}{2} ln ∣ tan (x) + sec (x) ∣) : - x sec^{3} (x) cos^{3} (x) + x + \frac{1}{2} sec (x) tan (x) + \frac{1}{2} ln ∣ tan (x) + sec (x) ∣

= - x sec^{3} (x) cos^{3} (x) + x + \frac{1}{2} sec (x) tan (x) + \frac{1}{2} ln ∣ tan (x) + sec (x) ∣

定数を解答に追加する

= - x sec^{3} (x) cos^{3} (x) + x + \frac{1}{2} sec (x) tan (x) + \frac{1}{2} ln ∣ tan (x) + sec (x) ∣ + C