integral of (cos(2x))/(cos(x))

解

\int \frac{cos ( 2 x )}{cos ( x )} d x

- ln ∣ tan (x) + sec (x) ∣ + 2 sin (x) + C

解答ステップ

\int \frac{cos ( 2 x )}{cos ( x )} d x

三角関数の公式を使用して書き換える

= \int \frac{- 1 + 2 cos ^{2} ( x )}{cos ( x )} d x

拡張

\frac{- 1 + 2 cos ^{2} ( x )}{cos ( x )} : - \frac{1}{cos ( x )} + 2 cos (x)

= \int - \frac{1}{cos ( x )} + 2 cos (x) d x

総和規則を適用する:

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

= - \int \frac{1}{cos ( x )} d x + \int 2 cos (x) d x

\int \frac{1}{cos ( x )} d x = ln ∣ tan (x) + sec (x) ∣

\int 2 cos (x) d x = 2 sin (x)

= - ln ∣ tan (x) + sec (x) ∣ + 2 sin (x)

定数を解答に追加する

= - ln ∣ tan (x) + sec (x) ∣ + 2 sin (x) + C