Recognize standard form: Recognize the integral as a standard form. The integral ∫9−4x21dx resembles the integral of the form ∫a2−x21dx, which is a standard form for the inverse trigonometric function arcsin(ax).
Identify a2: Identify a2 from the integral.In our integral, a2=9, so a=3. This means we can rewrite the integral in terms of a standard extarcsin function.
Use substitution x=23sin(u): Rewrite the integral using the substitution x=23sin(u). Let x=23sin(u), then dx=23cos(u)du. We need to find the limits of integration in terms of u, but since this is an indefinite integral, we will just perform the substitution.
Substitute x and dx: Substitute x and dx in the integral.Substituting x and dx into the integral, we get ∫9−4(23sin(u))21⋅(23)cos(u)du.
Simplify expression: Simplify the integral.Simplify the expression under the square root: 9−4(23)2sin2(u)=9−9sin2(u)=9(1−sin2(u))=9cos2(u).The integral becomes ∫9cos2(u)1⋅(23)cos(u)du.
Further simplify integral: Further simplify the integral.Since 9cos2(u)=3cos(u), the integral simplifies to ∫3cos(u)1⋅(23)cos(u)du=∫21du.
Integrate with respect to u: Integrate with respect to u. The integral of 21 with respect to u is (21)u+C.
Substitute back for u: Substitute back for u.We need to express our answer in terms of x, so we substitute back using the original substitution x=23sin(u). We solve for u: sin(u)=32x, so u=arcsin(32x).
Write final answer: Write the final answer.The final answer is (21)arcsin(32x)+C.
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