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Obtain the Fourier series of the function defined by f(x) = x², -1 <= x <= 1. Obtain the Fourier series of the function defined by f(t) = 1 + t/4, -4 <= t <= 0; 1 - t/4, 0 <= t <= 4 . Sketch f(t) in the interval -8 <= t <= 8. Determine the Fourier series expansion of f(t).

Mathematics

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Answers

2 parts
a

Δf(x)=3x2+3x+1\Delta f(x) = 3x^{2} + 3x + 1

b

Δf(x)=(a−1)ax\Delta f(x) = (a-1)a^{x}

Step-by-step solution

11 steps

Part a· 5 steps

  1. The forward difference is defined as

    Δf(x)=f(x+1)−f(x).\Delta f(x) = f(x+1) - f(x).
  2. For f(x)=x3f(x) = x^3, first find f(x+1)f(x+1)

    f(x+1)=(x+1)3.f(x+1) = (x+1)^3.
  3. Expand (x+1)3(x+1)^3 using the binomial theorem

    (x+1)3=x3+3x2(1)+3x(1)2+(1)3=x3+3x2+3x+1.(x+1)^3 = x^3 + 3x^2(1) + 3x(1)^2 + (1)^3 = x^3 + 3x^2 + 3x + 1.
  4. Substitute into the difference formula

    Δf(x)=(x3+3x2+3x+1)−x3.\Delta f(x) = (x^3 + 3x^2 + 3x + 1) - x^3.
  5. Simplify

    Δf(x)=3x2+3x+1.\Delta f(x) = 3x^2 + 3x + 1. Δf(x)=3x2+3x+1\boxed{\Delta f(x) = 3x^{2} + 3x + 1}

Part b

Δf(x)=(a−1)ax\Delta f(x) = (a-1)a^{x}

  1. The forward difference is defined as

    Δf(x)=f(x+1)−f(x).\Delta f(x) = f(x+1) - f(x).
  2. For f(x)=axf(x) = a^{x} where a>0a > 0, a≠1a \neq 1, first find f(x+1)f(x+1)

    f(x+1)=ax+1.f(x+1) = a^{x+1}.
  3. Rewrite ax+1a^{x+1}

    ax+1=a⋅ax.a^{x+1} = a \cdot a^{x}.
  4. Substitute into the difference formula

    Δf(x)=a⋅ax−ax.\Delta f(x) = a \cdot a^{x} - a^{x}.
  5. Factor out the common term axa^{x}

    Δf(x)=ax(a−1).\Delta f(x) = a^{x}(a - 1).
  6. Note that this can also be written as

    Δf(x)=(a−1)f(x),\Delta f(x) = (a-1) f(x),

    since f(x)=axf(x) = a^{x}.

    Δf(x)=(a−1)ax\boxed{\Delta f(x) = (a-1)a^{x}}
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