### 3.128 $$\int \sqrt{1-4 x^2} \, dx$$

Optimal. Leaf size=25 $\frac{1}{2} \sqrt{1-4 x^2} x+\frac{1}{4} \sin ^{-1}(2 x)$

[Out]

(x*Sqrt[1 - 4*x^2])/2 + ArcSin[2*x]/4

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Rubi [A]  time = 0.0034196, antiderivative size = 25, normalized size of antiderivative = 1., number of steps used = 2, number of rules used = 2, integrand size = 11, $$\frac{\text{number of rules}}{\text{integrand size}}$$ = 0.182, Rules used = {195, 216} $\frac{1}{2} \sqrt{1-4 x^2} x+\frac{1}{4} \sin ^{-1}(2 x)$

Antiderivative was successfully veriﬁed.

[In]

Int[Sqrt[1 - 4*x^2],x]

[Out]

(x*Sqrt[1 - 4*x^2])/2 + ArcSin[2*x]/4

Rule 195

Int[((a_) + (b_.)*(x_)^(n_))^(p_), x_Symbol] :> Simp[(x*(a + b*x^n)^p)/(n*p + 1), x] + Dist[(a*n*p)/(n*p + 1),
Int[(a + b*x^n)^(p - 1), x], x] /; FreeQ[{a, b}, x] && IGtQ[n, 0] && GtQ[p, 0] && (IntegerQ[2*p] || (EqQ[n, 2
] && IntegerQ[4*p]) || (EqQ[n, 2] && IntegerQ[3*p]) || LtQ[Denominator[p + 1/n], Denominator[p]])

Rule 216

Int[1/Sqrt[(a_) + (b_.)*(x_)^2], x_Symbol] :> Simp[ArcSin[(Rt[-b, 2]*x)/Sqrt[a]]/Rt[-b, 2], x] /; FreeQ[{a, b}
, x] && GtQ[a, 0] && NegQ[b]

Rubi steps

\begin{align*} \int \sqrt{1-4 x^2} \, dx &=\frac{1}{2} x \sqrt{1-4 x^2}+\frac{1}{2} \int \frac{1}{\sqrt{1-4 x^2}} \, dx\\ &=\frac{1}{2} x \sqrt{1-4 x^2}+\frac{1}{4} \sin ^{-1}(2 x)\\ \end{align*}

Mathematica [A]  time = 0.0070851, size = 25, normalized size = 1. $\frac{1}{2} \sqrt{1-4 x^2} x+\frac{1}{4} \sin ^{-1}(2 x)$

Antiderivative was successfully veriﬁed.

[In]

Integrate[Sqrt[1 - 4*x^2],x]

[Out]

(x*Sqrt[1 - 4*x^2])/2 + ArcSin[2*x]/4

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Maple [A]  time = 0.004, size = 20, normalized size = 0.8 \begin{align*}{\frac{\arcsin \left ( 2\,x \right ) }{4}}+{\frac{x}{2}\sqrt{-4\,{x}^{2}+1}} \end{align*}

Veriﬁcation of antiderivative is not currently implemented for this CAS.

[In]

int((-4*x^2+1)^(1/2),x)

[Out]

1/4*arcsin(2*x)+1/2*x*(-4*x^2+1)^(1/2)

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Maxima [A]  time = 1.40291, size = 26, normalized size = 1.04 \begin{align*} \frac{1}{2} \, \sqrt{-4 \, x^{2} + 1} x + \frac{1}{4} \, \arcsin \left (2 \, x\right ) \end{align*}

Veriﬁcation of antiderivative is not currently implemented for this CAS.

[In]

integrate((-4*x^2+1)^(1/2),x, algorithm="maxima")

[Out]

1/2*sqrt(-4*x^2 + 1)*x + 1/4*arcsin(2*x)

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Fricas [A]  time = 1.98043, size = 90, normalized size = 3.6 \begin{align*} \frac{1}{2} \, \sqrt{-4 \, x^{2} + 1} x - \frac{1}{2} \, \arctan \left (\frac{\sqrt{-4 \, x^{2} + 1} - 1}{2 \, x}\right ) \end{align*}

Veriﬁcation of antiderivative is not currently implemented for this CAS.

[In]

integrate((-4*x^2+1)^(1/2),x, algorithm="fricas")

[Out]

1/2*sqrt(-4*x^2 + 1)*x - 1/2*arctan(1/2*(sqrt(-4*x^2 + 1) - 1)/x)

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Sympy [A]  time = 0.186725, size = 19, normalized size = 0.76 \begin{align*} \frac{x \sqrt{1 - 4 x^{2}}}{2} + \frac{\operatorname{asin}{\left (2 x \right )}}{4} \end{align*}

Veriﬁcation of antiderivative is not currently implemented for this CAS.

[In]

integrate((-4*x**2+1)**(1/2),x)

[Out]

x*sqrt(1 - 4*x**2)/2 + asin(2*x)/4

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Giac [A]  time = 1.05781, size = 26, normalized size = 1.04 \begin{align*} \frac{1}{2} \, \sqrt{-4 \, x^{2} + 1} x + \frac{1}{4} \, \arcsin \left (2 \, x\right ) \end{align*}

Veriﬁcation of antiderivative is not currently implemented for this CAS.

[In]

integrate((-4*x^2+1)^(1/2),x, algorithm="giac")

[Out]

1/2*sqrt(-4*x^2 + 1)*x + 1/4*arcsin(2*x)