Q. Evaluate the integral and express your answer in simplest form.∫25−9x2−1dxAnswer:
Given Integral: We are given the integral: ∫25−9x2−1dxTo solve this integral, we can use a trigonometric substitution. Let's choose x=35sin(θ), because the expression 25−9x2 resembles a Pythagorean identity when x is expressed in terms of sine.
Trigonometric Substitution: Differentiate x=35sin(θ) with respect to θ to find dx:dθdx=35cos(θ)dx=35cos(θ)dθ
Differentiate x: Substitute x=35sin(θ) and dx=35cos(θ)dθ into the integral:∫25−9x2−1dx=∫25−9(35)2sin2(θ)−1(35)cos(θ)dθSimplify the expression inside the square root:25−9(35)2sin2(θ)=25−25sin2(θ)=25(1−sin2(θ))
Substitute x and dx: Recognize that 1−sin2(θ) is equal to cos2(θ) by the Pythagorean identity:25(1−sin2(θ))=25cos2(θ)Now, substitute this back into the integral:∫(−1)/(25−9∗(5/3)2sin2(θ))∗(5/3)cos(θ)dθ=∫(−1)/(25cos2(θ))∗(5/3)cos(θ)dθ
Simplify Expression: Simplify the integral by taking the square root of 25cos2(θ), which is 5cos(θ):∫5cos(θ)−1(35cos(θ))dθThe cos(θ) terms cancel out, and we are left with:∫(−31)dθ
Recognize Identity: Integrate −31 with respect to θ:∫(−31)dθ=−31×θ+C
Simplify Integral: Now we need to express θ back in terms of x. Since x=35sin(θ), we can solve for θ using the inverse sine function:sin(θ)=53xθ=arcsin(53x)Substitute θ back into the integral result:−31⋅θ+C=−31⋅arcsin(53x)+C
More problems from Find indefinite integrals using the substitution