Identify Integral: Let's identify the integral we need to solve:I=∫xx2−362dxWe can see that this integral suggests a trigonometric substitution because of the form a2−x2 under the square root. We will use the substitution x=asec(θ), where a=6 in this case, because 36=62.
Substitute x: Substitute x=6sec(θ) into the integral. Then, dx=6sec(θ)tan(θ)dθ and x2−36=36sec2(θ)−36=36(tan2(θ)). The integral becomes:I=∫6sec(θ)36tan2(θ)2⋅6sec(θ)tan(θ)dθ
Simplify Integral: Simplify the integral by canceling terms and using the identity tan2(θ)=∣tan(θ)∣. Since we are dealing with x > 6 (because of the original square root), \sec(\theta) > 0, and thus \tan(\theta) > 0, we can remove the absolute value:I=∫6sec(θ)tan(θ)2⋅6sec(θ)tan(θ)dθI=∫2dθ
Integrate with θ: Integrate with respect to θ:I=2θ+C, where C is the constant of integration.
Substitute back for θ: We need to substitute back for θ using our original substitution x=6sec(θ). We have sec(θ)=6x, and to find θ, we use the definition of secant: sec(θ)=cos(θ)1, so cos(θ)=x6. Then θ=cos−1(x6). I=2cos−1(x6)+C
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