Natural domain of a function of one variable

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Find the domain of the following function: y=x21+xy=\dfrac {x^{2}}{1+x}.

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Find the domain of the following function: y=3x−x3y=\sqrt{3x-x^{3}}.

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Find the domain of the following function: y=(x−2)1+x1−xy=(x-2)\sqrt{\dfrac {1+x}{1-x}}.

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Find the domain of the following functions:

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(a)

y=log⁡(x2−4)y=\log (x^{2}-4);

(b)

y=log⁡(x+2)+log⁡(x−2)y=\log (x+2)+\log (x-2).

Find the domain of the following function: y=sin⁡(x)y=\sqrt{\sin (\sqrt{x})}.

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Find the domain of the following function: y=cos⁡x2y=\sqrt{\cos x^{2}}.

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Find the domain of the following function: y=log⁡(sin⁡πx)y=\log \left(\sin \dfrac {\pi }{x}\right).

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Find the domain of the following function: y=xsin⁡πxy=\dfrac {\sqrt{x}}{\sin \pi x}.

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Find the domain of the following function: y=arcsin⁡2x1+xy=\arcsin \dfrac {2x}{1+x}.

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Find the domain of the following function: y=arccos⁡(2sin⁡x)y=\arccos (2\sin x).

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Find the domain of the following function: y=lg⁡[cos⁡(lg⁡x)]y=\lg [\cos (\lg x)].

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Find the domain of the following function: y=(x−∣x∣)−sin⁡2πxy=(x-\left|x\right|)\sqrt{-\sin^{2}\pi x}.

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Find the domain of the following function: y=ctg⁡πx+arccos⁡(2x)y=\operatorname {ctg}\pi x+\arccos (2^{x}).

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Find the domain of the following function: y=arcsin⁡(1−x)+lg⁡(lg⁡x)y=\arcsin (1-x)+\lg (\lg x).

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Find the domain of the following function: y=(2x)!y=(2x)!.

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Suppose the function f(u)f(u) is defined for 0<u<10<u<1, find the domain of each of the following functions:

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(a)

f(sin⁡x)f(\sin x);

(b)

f(ln⁡x)f(\ln x);

(c)

f([x]x)f\left(\dfrac {[x]}{x}\right).

Find the domain of the function given by the formula.

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(1)

y=xx+1y = \frac{x}{x+1}

(2)

y=x+1x2−1y = \frac{x+1}{x^{2}-1}

(3)

y=x3−1x2−6x+8y = \frac{x^{3}-1}{x^{2}-6 x+8}

(4)

y=(x+2)2x3−4xy = \frac{(x+2)^{2}}{x^{3}-4 x}

(5)

y=1x+∣x∣y = \frac{1}{x+\left|x\right|};

(6)

y=x22∣x∣−3y = \frac{x^{2}}{2\left|x\right|-3};

(7)

y=∣x+2∣+1−2x−2x2∣2x+2∣−1y = \frac{\left|x+2\right|+1-2 x-2 x^{2}}{\left|2 x+2\right|-1}.

Find the domain of the function given by the formula.

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(1)

y=x2−13y = \sqrt[3]{x^{2}-1};

(2)

y=−x2y = \sqrt{-x^{2}}

(3)

y=2−x4y = \sqrt[4]{2-x}

(4)

y=2−x−x2y = \sqrt{2-x-x^{2}}

(5)

y=11−x2y = \frac{1}{\sqrt{1-x^{2}}};

(6)

y=x2−16xy = \frac{\sqrt[6]{x^{2}-1}}{x};

(7)

y=x(9−x2)2/3y = \frac{x}{\left(9-x^{2}\right)^{2 / 3}};

(8)

y=x2(x−2)y = \sqrt{x^{2}(x-2)};

(9)

y=x−31−3x+2x2y = \sqrt{\frac{x-3}{1-3 x+2 x^{2}}}.

Find the domains of the functions f1,f2,f1+f2f_{1}, f_{2}, f_{1}+f_{2}, if f1f_{1} and f2f_{2} are given by the formulas:

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(1)

f1(x)=3−x4,f2(x)=x+1f_{1}(x) = \sqrt[4]{3-x}, f_{2}(x) = \sqrt{x+1};

(2)

f1(x)=1−x2,f2(x)=x2x−13f_{1}(x) = \sqrt{1-x^{2}}, f_{2}(x) = \sqrt[3]{\frac{x}{2 x-1}}

(3)

f1(x)=x−x−3,f2(x)=lg⁡(x2−4)f_{1}(x) = \sqrt{x}-\sqrt{x-3}, f_{2}(x) = \lg \left(x^{2}-4\right);

(4)

f1(x)=15x−x24,f2(x)=tg⁡(x)f_{1}(x) = \frac{1}{\sqrt[4]{5 x-x^{2}}}, f_{2}(x) = \operatorname {tg}(x);

(5)

f1(x)=lg⁡(16−x2),f2(x)=11−sin⁡xf_{1}(x) = \lg \left(16-x^{2}\right), f_{2}(x) = \frac{1}{1-\sin x};

(6)

f1(x)=x+x−1,f2(x)=x−x−1f_{1}(x) = x+\sqrt{x-1}, f_{2}(x) = x-\sqrt{x-1}.

Find the domains of the functions ff and 1/f1 / f, if ff is given by the formula:

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(1)

f(x)=x2−x+1f(x) = x^{2}-x+1

(2)

f(x)=∣x∣−2f(x) = \left|x\right|-2

(3)

f(x)=lg⁡(1−x2)f(x) = \lg \left(1-x^{2}\right);

(4)

f(x)=x+x+2f(x) = x+\sqrt{x+2}

(5)

f(x)=2x+1−x+1f(x) = \sqrt{2 x+1}-\sqrt{x+1}

(6)

f(x)=5x−2x+1f(x) = 5^{x}-2^{x+1}

(7)

f(x)=3−2cos⁡xf(x) = 3-2 \cos x

(8)

f(x)=2−2sin⁡xf(x) = \sqrt{2}-2 \sin x

(9)

f(x)=1−ctg⁡xf(x) = 1-\operatorname {ctg} x.

Find the compositions f∘gf \circ g and g∘fg \circ f and indicate their domains for the functions given by the formulas:

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(1)

f(x)=x2,g(x)=xf(x) = x^{2}, g(x) = \sqrt{x}

(2)

f(x)=g(x)=1−x2f(x) = g(x) = \sqrt{1-x^{2}};

(3)

f(x)=10x,g(x)=lg⁡xf(x) = 10^{x}, g(x) = \lg x

(4)

f(x)=x5,g(x)=x+5f(x) = x^{5}, g(x) = x+5;

(5)

f(x)={x,x∈[0;+∞)0,x∈(−∞;0)f(x) = \begin{cases} x, & x \in [0 ;+\infty ) \\ 0, & x \in (-\infty ; 0)\end{cases}, g(x)={0,x∈[0;+∞),x2,x∈(−∞;0);g(x) = \begin{cases} 0, & x \in [0 ;+\infty ), \\ x^{2}, & x \in (-\infty ; 0) ; \end{cases}

(6)

f(x)=ln⁡x2,g(x)=sin⁡xf(x) = \ln x^{2}, g(x) = \sin x.

Find the domain of the function:

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(1)

y=116x2−2xy = \frac{1}{16^{x^{2}}-2^{x}}

(2)

y=2x−3xy = \sqrt{2^{x}-3^{x}}

(3)

y=log⁡2x2y = \log_{2} x^{2} and y=2log⁡2xy = 2 \log_{2} x;

(4)

y=log⁡x5y = \log_{x} 5;

(5)

y=(lg⁡(100−x))−1y = (\lg (100-x))^{-1};

(6)

y=ln⁡x+ln⁡(x−1)y = \ln x+\ln (x-1) and y=ln⁡x(x−1)y = \ln x(x-1);

(7)

y=log⁡3+x(x2−1)y = \log_{3+x}\left(x^{2}-1\right);

(8)

y=log⁡3log⁡0,5xy = \log_{3} \log_{0,5} x.

Find the domain of the function.

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(1)

y=x6−xy = \sqrt{\frac{x}{6-x}};

(2)

y=3−5x−2x2y = \sqrt{3-5 x-2 x^{2}};

(3)

y=x1−∣x∣3y = \sqrt[3]{\frac{x}{1-\left|x\right|}};

(4)

y=x2−∣x∣−2y = \sqrt{x^{2}-\left|x\right|-2}

(5)

y=3+x4+3−x4y = \sqrt[4]{3+x}+\sqrt[4]{3-x}

(6)

y=(8−2x−x2)−3/2y = \left(8-2 x-x^{2}\right)^{-3 / 2}.

Find the domain of the function.

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(1)

y=lg⁡(x2+1)y = \lg \left(x^{2}+1\right);

(2)

y=x+2lg⁡cos⁡x3y = \sqrt[3]{\frac{x+2}{\lg \cos x}};

(3)

y=lg⁡3x−x2x−1y = \lg \frac{3 x-x^{2}}{x-1}

(4)

y=log⁡32x−3x−1y = \sqrt{\log_{3} \frac{2 x-3}{x-1}};

(5)

y=x+5lg⁡(9−5x)y = \frac{\sqrt{x+5}}{\lg (9-5 x)};

(6)

y=x2−4log⁡2(x2+2x−3)y = \frac{\sqrt{x^{2}-4}}{\log_{2}\left(x^{2}+2 x-3\right)};

(7)

y=log⁡x+1(x2−3x+2)y = \log_{x+1}\left(x^{2}-3 x+2\right);

(8)

y=log⁡xlog⁡0,5(43−2x−1)y = \log_{x} \log_{0,5}\left(\frac{4}{3}-2^{x-1}\right);

(9)

y=lg⁡(1,251−x2−0,40961+x)y = \lg \left(1,25^{1-x^{2}}-0,4096^{1+x}\right);

(10)

y=ln⁡(1−lg⁡(x2−5x+16))y = \ln \left(1-\lg \left(x^{2}-5 x+16\right)\right).

References

[Dem97] Demidovich B.P. Сборник задач и упражнений по математическому анализу. 13-е изд., Издательство Московского университета / Издательство "ЧеРо", 1997.
[ККЧ+03] Кудрявцев Л.Д., Кутасов А.Д., Чехлов В.И., Шабунин М.И. Предел. Непрерывность. Дифференцируемость. 2-е изд., ФИЗМАТЛИТ, 2003.