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受欢迎的微积分 >

integral of 2(cos(x))^2

解答

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

解答

x + \frac{1}{2} sin (2 x) + C

求解步骤

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

提出常数:

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

= 2 \cdot \int (cos (x))^{2} d x

化简

= 2 \cdot \int cos^{2} (x) d x

使用三角恒等式改写

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

提出常数:

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

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

使用积分加法定则:

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

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

\int 1 d x = x

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

= 2 \cdot \frac{1}{2} (x + \frac{1}{2} sin (2 x))

化简

2 \cdot \frac{1}{2} (x + \frac{1}{2} sin (2 x)) : x + \frac{1}{2} sin (2 x)

= x + \frac{1}{2} sin (2 x)

解答补常数

= x + \frac{1}{2} sin (2 x) + C

作图

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