Methods in calculus Worked Solutions — Further Maths Maths

Fully worked, step-by-step solutions to Further Maths Methods in calculus questions. See exactly how to solve problems on improper-integrals, power-rule, exponential-integration, mean-value.

improper-integralspower-ruleexponential-integrationmean-valuepolynomial-integrationinverse-tangent-integral
Further Maths70 questionsStep-by-step solutions
Question 1
2 markseasy
Evaluate 11x2dx\int_{1}^{\infty}\frac{1}{x^{2}}\,dx.

Worked solution

  1. Write down the integral to be evaluated

    I=11x2dxI=\int_{1}^{\infty}\frac{1}{x^{2}}\,dx

    Identify the integrand and the limits of integration.

  2. State why the integral is improper

    improper: unbounded interval\text{improper: }\text{unbounded interval}

    This integral is improper because the upper limit is infinite.

  3. State the final answer

    I=1I=1

    This is the exact value required.

Answer
11
Question 2
2 markseasy
Evaluate 21x3dx\int_{2}^{\infty}\frac{1}{x^{3}}\,dx.

Worked solution

  1. Write down the integral to be evaluated

    I=21x3dxI=\int_{2}^{\infty}\frac{1}{x^{3}}\,dx

    Identify the integrand and the limits of integration.

  2. State why the integral is improper

    improper: unbounded interval\text{improper: }\text{unbounded interval}

    This integral is improper because the upper limit is infinite.

  3. State the final answer

    I=18I=\frac{1}{8}

    This is the exact value required.

Answer
18\frac{1}{8}
Question 3
2 markseasy
Evaluate 11x4dx\int_{1}^{\infty}\frac{1}{x^{4}}\,dx.

Worked solution

  1. Write down the integral to be evaluated

    I=11x4dxI=\int_{1}^{\infty}\frac{1}{x^{4}}\,dx

    Identify the integrand and the limits of integration.

  2. State why the integral is improper

    improper: unbounded interval\text{improper: }\text{unbounded interval}

    This integral is improper because the upper limit is infinite.

  3. Replace the offending limit by tt and take a limit

    11x4dx=limt1t1x4dx\int_{1}^{\infty}\frac{1}{x^{4}}\,dx=\lim_{t\to\infty}\int_{1}^{t}\frac{1}{x^{4}}\,dx

    The improper integral is DEFINED as this limit; it is not a substitution.

  4. State the final answer

    I=13I=\frac{1}{3}

    This is the exact value required.

Answer
13\frac{1}{3}
Question 4
2 markseasy
Evaluate 091xdx\int_{0}^{9}\frac{1}{\sqrt{x}}\,dx.

Worked solution

  1. Write down the integral to be evaluated

    I=091xdxI=\int_{0}^{9}\frac{1}{\sqrt{x}}\,dx

    Identify the integrand and the limits of integration.

  2. State why the integral is improper

    improper: f(x) as x0\text{improper: }f(x)\to\infty\text{ as }x\to0

    This integral is improper because the integrand is undefined at x=0x=0.

  3. State the final answer

    I=6I=6

    This is the exact value required.

Answer
66
Question 5
2 markseasy
Evaluate 041xdx\int_{0}^{4}\frac{1}{\sqrt{x}}\,dx.

Worked solution

  1. Write down the integral to be evaluated

    I=041xdxI=\int_{0}^{4}\frac{1}{\sqrt{x}}\,dx

    Identify the integrand and the limits of integration.

  2. State why the integral is improper

    improper: f(x) as x0\text{improper: }f(x)\to\infty\text{ as }x\to0

    This integral is improper because the integrand is undefined at x=0x=0.

  3. State the final answer

    I=4I=4

    This is the exact value required.

Answer
44

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