Q. Evaluate the integral and express your answer in simplest form.∫16−4x210dxAnswer:
Substitution: We are given the integral: ∫16−4x210dxTo solve this integral, we can use a trigonometric substitution. Let's choose x=2sin(θ), because the expression under the square root resembles the Pythagorean identity 1−sin2(θ)=cos2(θ). This will simplify the square root.
Differentiation: First, we need to find dx in terms of d(θ). Differentiating x=2sin(θ) with respect to θ gives us:d(θ)dx=2cos(θ)Therefore, dx=2cos(θ)d(θ)
Integral Substitution: Now, we substitute x=2sin(θ) and dx=2cos(θ)d(θ) into the integral:∫16−4x210dx=∫16−4(2sin(θ))210⋅2cos(θ)d(θ)Simplify the expression under the square root:∫16−4(4sin2(θ))10⋅2cos(θ)d(θ)=∫16−16sin2(θ)10⋅2cos(θ)d(θ)
Simplify Expression: The expression under the square root simplifies to 16cos2(θ), using the Pythagorean identity:∫(16−16sin2(θ)10)⋅2cos(θ)d(θ)=∫(16cos2(θ)10)⋅2cos(θ)d(θ)Simplify the square root:∫(4cos(θ)10)⋅2cos(θ)d(θ)=∫(410⋅cos(θ)2cos(θ))d(θ)
Integrate with Respect: The cos(θ) terms cancel out, leaving us with:∫(410⋅2)d(θ)=∫(5)d(θ)Now, integrate with respect to theta:∫(5)d(θ)=5θ+C
Final Answer: We need to express the answer in terms of x, so we have to substitute back for θ using our original substitution x=2sin(θ). To find θ, we use the inverse sine function:θ=arcsin(2x)So the integral in terms of x is:5θ+C=5arcsin(2x)+C
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