Q. Evaluate the integral and express your answer in simplest form.∫4−16x2−3dxAnswer:
Given Integral: We are given the integral: ∫4−16x2−3dxTo solve this integral, we can use a trigonometric substitution. Let's choose x=21sin(θ), because the expression 4−16x2 resembles a Pythagorean identity when x is expressed in terms of sine.
Trigonometric Substitution: First, we need to find dx in terms of dθ. Differentiating x=21sin(θ) with respect to θ, we get:dθdx=21cos(θ)Therefore, dx=21cos(θ)dθ
Finding dx: Now, we substitute x=21sin(θ) and dx=21cos(θ)d(θ) into the integral:∫4−16x2−3dx=∫4−16(21sin(θ))2−3(21cos(θ))d(θ)Simplify the expression inside the square root:=∫4−4sin2(θ)−3(21cos(θ))d(θ)=∫4(1−sin2(θ))−3(21cos(θ))d(θ)
Substitute x and dx: Recognize that 1−sin2(θ) is equal to cos2(θ) due to the Pythagorean identity. So we can further simplify the integral:=∫4cos2(θ)−3(21)cos(θ)d(θ)=∫2∣cos(θ)∣−3(21)cos(θ)d(θ)Since θ is the arcsine of x, and we are dealing with a square root, we can assume that cos(θ) is positive in the range we are considering.=∫2cos(θ)−3(21)cos(θ)d(θ)=∫(−43)d(θ)
Simplify Expression: Now we can integrate with respect to θ: ∫(−43)d(θ)=(−43)θ+C
Integrate with respect to theta: We need to express θ back in terms of x. Since x=21sin(θ), we have θ=arcsin(2x). So we substitute back: −43θ+C=−43arcsin(2x)+C
Express θ in terms of x: We have found the indefinite integral in terms of x: ∫4−16x2−3dx=(−43)arcsin(2x)+C
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