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Evaluate the integral and express your answer in simplest form.

int(-1)/(sqrt(25-9x^(2)))dx
Answer:

Evaluate the integral and express your answer in simplest form.\newline1259x2dx \int \frac{-1}{\sqrt{25-9 x^{2}}} d x \newlineAnswer:

Full solution

Q. Evaluate the integral and express your answer in simplest form.\newline1259x2dx \int \frac{-1}{\sqrt{25-9 x^{2}}} d x \newlineAnswer:
  1. Given Integral: We are given the integral: \newline1259x2dx\int \frac{-1}{\sqrt{25-9x^{2}}}dx\newlineTo solve this integral, we can use a trigonometric substitution. Let's choose x=53sin(θ)x = \frac{5}{3}\sin(\theta), because the expression 259x225 - 9x^2 resembles a Pythagorean identity when xx is expressed in terms of sine.
  2. Trigonometric Substitution: Differentiate x=53sin(θ)x = \frac{5}{3}\sin(\theta) with respect to θ\theta to find dxdx:dxdθ=53cos(θ)\frac{dx}{d\theta} = \frac{5}{3}\cos(\theta)dx=53cos(θ)dθdx = \frac{5}{3}\cos(\theta)d\theta
  3. Differentiate xx: Substitute x=53sin(θ)x = \frac{5}{3}\sin(\theta) and dx=53cos(θ)dθdx = \frac{5}{3}\cos(\theta)d\theta into the integral:\newline1259x2dx=1259(53)2sin2(θ)(53)cos(θ)dθ\int \frac{-1}{\sqrt{25-9x^{2}}}dx = \int \frac{-1}{\sqrt{25-9\left(\frac{5}{3}\right)^2\sin^2(\theta)}}\left(\frac{5}{3}\right)\cos(\theta)d\theta\newlineSimplify the expression inside the square root:\newline259(53)2sin2(θ)=2525sin2(θ)=25(1sin2(θ))25 - 9\left(\frac{5}{3}\right)^2\sin^2(\theta) = 25 - 25\sin^2(\theta) = 25(1 - \sin^2(\theta))
  4. Substitute xx and dxdx: Recognize that 1sin2(θ)1 - \sin^2(\theta) is equal to cos2(θ)\cos^2(\theta) by the Pythagorean identity:\newline25(1sin2(θ))=25cos2(θ)25(1 - \sin^2(\theta)) = 25\cos^2(\theta)\newlineNow, substitute this back into the integral:\newline(1)/(259(5/3)2sin2(θ))(5/3)cos(θ)dθ=(1)/(25cos2(θ))(5/3)cos(θ)dθ\int(-1)/(\sqrt{25-9*(5/3)^2\sin^2(\theta)})*(5/3)\cos(\theta)d\theta = \int(-1)/(\sqrt{25\cos^2(\theta)})*(5/3)\cos(\theta)d\theta
  5. Simplify Expression: Simplify the integral by taking the square root of 25cos2(θ)25\cos^2(\theta), which is 5cos(θ)5\cos(\theta):\newline15cos(θ)(53cos(θ))dθ\int\frac{-1}{5\cos(\theta)}\left(\frac{5}{3}\cos(\theta)\right)d\theta\newlineThe cos(θ)\cos(\theta) terms cancel out, and we are left with:\newline(13)dθ\int\left(-\frac{1}{3}\right)d\theta
  6. Recognize Identity: Integrate 13-\frac{1}{3} with respect to θ\theta:(13)dθ=13×θ+C\int\left(-\frac{1}{3}\right)d\theta = -\frac{1}{3} \times \theta + C
  7. Simplify Integral: Now we need to express θ\theta back in terms of xx. Since x=53sin(θ)x = \frac{5}{3}\sin(\theta), we can solve for θ\theta using the inverse sine function:\newlinesin(θ)=35x\sin(\theta) = \frac{3}{5}x\newlineθ=arcsin(35x)\theta = \arcsin(\frac{3}{5}x)\newlineSubstitute θ\theta back into the integral result:\newline13θ+C=13arcsin(35x)+C-\frac{1}{3} \cdot \theta + C = -\frac{1}{3} \cdot \arcsin(\frac{3}{5}x) + C