In this section, we explore the integration of certain functions related to inverse trigonometric functions, leveraging the relationship between derivatives and integrals. Understanding these integrals is crucial, as they often arise in calculus problems where standard integration techniques may not suffice.
We begin with the integral of the function 1 / √(1 - x²). Recognizing that the derivative of the inverse sine function, sin-1(x), is 1 / √(1 - x²), we can conclude that:
$$\int \frac{1}{\sqrt{1 - x^2}} \, dx = \sin^{-1}(x) + C$$
Here, C represents the constant of integration. For example, when integrating 4 / √(1 - x²), we can factor out the constant:
$$\int \frac{4}{\sqrt{1 - x^2}} \, dx = 4 \cdot \sin^{-1}(x) + C$$
Next, we consider the integral of 1 / (1 + x²). The derivative of the inverse tangent function, tan-1(x), is 1 / (1 + x²), leading to the integral:
$$\int \frac{1}{1 + x^2} \, dx = \tan^{-1}(x) + C$$
For a more complex example, such as 1 / (1 + x²) + 1 / x², we can integrate each term separately. The first term gives us tan-1(x), while the second term can be rewritten as x-2, allowing us to apply the power rule:
$$\int \frac{1}{x^2} \, dx = -\frac{1}{x} + C$$
Thus, the combined result is:
$$\int \left(\frac{1}{1 + x^2} + \frac{1}{x^2}\right) \, dx = \tan^{-1}(x) - \frac{1}{x} + C$$
Finally, we examine the integral of 1 / (|x|√(x² - 1)). The derivative of the inverse secant function, sec-1(x), is 1 / (|x|√(x² - 1)), leading to:
$$\int \frac{1}{|x| \sqrt{x^2 - 1}} \, dx = \sec^{-1}(x) + C$$
For an example involving a constant, such as 1 / (3|x|√(x² - 1)), we can factor out the constant:
$$\int \frac{1}{3|x| \sqrt{x^2 - 1}} \, dx = \frac{1}{3} \sec^{-1}(x) + C$$
In summary, recognizing the derivatives of inverse trigonometric functions allows us to derive their corresponding integrals effectively. Memorizing these integral rules is beneficial, especially when encountering functions with 1 and x² in the denominator, as they often indicate the use of inverse trig functions. Continued practice with these integrals will enhance your proficiency in calculus.