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question:Sure, here's a numerical problem for a math student based on the subtopic "Finding the Fourier series of a function with a periodic discontinuity": Given a periodic function f(x) with a period of 2π that is defined as f(x) = 2 for -π < x < 0 and f(x) = -1 for 0 < x < π. Find the Fourier series of this function. The math student would need to use the formulas and techniques related to Fourier analysis to determine the coefficients of the Fourier series for this particular function, taking into account the periodic discontinuity in the interval (0, π).

answer:To find the Fourier series of the given function, we first need to find the coefficients a_n and b_n. The general form of a Fourier series is: f(x) = a_0/2 + Σ(a_n * cos(nx) + b_n * sin(nx)) where the summation is from n=1 to infinity. We can find a_0, a_n, and b_n using the following formulas: a_0 = (1/π) * ∫[f(x)]dx over the interval (-π, π) a_n = (1/π) * ∫[f(x) * cos(nx)]dx over the interval (-π, π) b_n = (1/π) * ∫[f(x) * sin(nx)]dx over the interval (-π, π) First, let's find a_0: a_0 = (1/π) * [∫(2)dx from -π to 0 + ∫(-1)dx from 0 to π] a_0 = (1/π) * [2x|(-π, 0) - x|(0, π)] a_0 = (1/π) * [2(0) - 2(-π) - (π - 0)] a_0 = (1/π) * (2π - π) a_0 = 1 Now, let's find a_n: a_n = (1/π) * [∫(2 * cos(nx))dx from -π to 0 + ∫(-1 * cos(nx))dx from 0 to π] a_n = (1/π) * [(2/n) * sin(nx)|(-π, 0) - (1/n) * sin(nx)|(0, π)] a_n = (1/π) * [(2/n) * (sin(0) - sin(-nπ)) - (1/n) * (sin(nπ) - sin(0))] a_n = (1/π) * [(2/n) * 0 - (1/n) * 0] a_n = 0 Finally, let's find b_n: b_n = (1/π) * [∫(2 * sin(nx))dx from -π to 0 + ∫(-1 * sin(nx))dx from 0 to π] b_n = (1/π) * [(-2/n) * cos(nx)|(-π, 0) + (1/n) * cos(nx)|(0, π)] b_n = (1/π) * [(-2/n) * (cos(0) - cos(-nπ)) + (1/n) * (cos(nπ) - cos(0))] b_n = (1/π) * [(-2/n) * (1 - (-1)^n) + (1/n) * ((-1)^n - 1)] For n = odd, b_n = (1/π) * [(-2/n) * (1 - (-1)) + (1/n) * ((-1) - 1)] = (1/π) * [(-2/n) * 2 + (1/n) * (-2)] = -4/nπ For n = even, b_n = 0 Now we can write the Fourier series for the given function: f(x) = 1/2 + Σ((-1)^((n-1)/2) * (4/nπ) * sin(nx)) for n odd, and 0 for n even This is the Fourier series representation of the given function with a periodic discontinuity.

question:Find the Fourier series of the function f(x) = 2x - 1 on the interval [0, 2π] with a periodic discontinuity at x = π.

answer:To find the Fourier series of the given function f(x) = 2x - 1 on the interval [0, 2π] with a periodic discontinuity at x = π, we need to compute the Fourier coefficients a_n and b_n for the sine and cosine terms. The general form of a Fourier series is: f(x) = a_0 + Σ[a_n * cos(n * x) + b_n * sin(n * x)] where the summation is from n = 1 to infinity, and a_0, a_n, and b_n are the Fourier coefficients. First, let's find the constant term a_0: a_0 = (1/π) * ∫[f(x)]dx from 0 to 2π Since the function has a periodic discontinuity at x = π, we need to split the integral into two parts: a_0 = (1/π) * [∫[f(x)]dx from 0 to π + ∫[f(x)]dx from π to 2π] For the interval [0, π], f(x) = 2x - 1: a_0 = (1/π) * [∫[(2x - 1)]dx from 0 to π + ∫[f(x)]dx from π to 2π] Now, for the interval [π, 2π], since the function is periodic with a discontinuity at x = π, we can write f(x) as f(x) = 2(x - π) - 1: a_0 = (1/π) * [∫[(2x - 1)]dx from 0 to π + ∫[(2(x - π) - 1)]dx from π to 2π] Now, we can evaluate the integrals: a_0 = (1/π) * [(x^2 - x)| from 0 to π + ((x^2 - 2πx + π^2 - x)| from π to 2π)] a_0 = (1/π) * [(π^2 - π) + (4π^2 - 4π^2 + π^2 - π)] a_0 = (1/π) * (π^2 - π) Now, let's find the coefficients a_n and b_n: a_n = (1/π) * ∫[f(x) * cos(n * x)]dx from 0 to 2π b_n = (1/π) * ∫[f(x) * sin(n * x)]dx from 0 to 2π Again, we need to split the integrals into two parts due to the periodic discontinuity at x = π: a_n = (1/π) * [∫[(2x - 1) * cos(n * x)]dx from 0 to π + ∫[(2(x - π) - 1) * cos(n * x)]dx from π to 2π] b_n = (1/π) * [∫[(2x - 1) * sin(n * x)]dx from 0 to π + ∫[(2(x - π) - 1) * sin(n * x)]dx from π to 2π] Now, we can integrate by parts: For a_n: Let u = 2x - 1, dv = cos(n * x)dx du = 2dx, v = (1/n) * sin(n * x) For b_n: Let u = 2x - 1, dv = sin(n * x)dx du = 2dx, v = -(1/n) * cos(n * x) Now, we can compute the integrals: a_n = (1/π) * [(u * v)| from 0 to π + (u * v)| from π to 2π - ∫[v * du] from 0 to 2π] a_n = (1/π) * [((2x - 1) * (1/n) * sin(n * x))| from 0 to π + ((2(x - π) - 1) * (1/n) * sin(n * x))| from π to 2π - (1/n) * ∫[sin(n * x) * 2]dx from 0 to 2π] b_n = (1/π) * [(u * v)| from 0 to π + (u * v)| from π to 2π - ∫[v * du] from 0 to 2π] b_n = (1/π) * [((2x - 1) * (-1/n) * cos(n * x))| from 0 to π + ((2(x - π) - 1) * (-1/n) * cos(n * x))| from π to 2π + (1/n) * ∫[cos(n * x) * 2]dx from 0 to 2π] Now, we can evaluate the integrals and simplify the expressions for a_n and b_n. Finally, we can write the Fourier series for the given function: f(x) = (π^2 - π)/π + Σ[a_n * cos(n * x) + b_n * sin(n * x)]

question:What is the Fourier series for the function f(x) whose domain is [-4,4] and is defined as follows: f(x) = begin{cases} 1 & text{if } -4 leq x < 0 0 & text{if } x = 0 -1 & text{if } 0 < x leq 4 end{cases} In other words, find the Fourier series for the function that is equal to 1 on the interval [-4,0), equal to 0 at x=0, and equal to -1 on the interval (0,4]. Recall that the Fourier series of a periodic function f(x) with period 2L is given by: f(x) = frac{a_0}{2} + sum_{n=1}^infty left[ a_n cosleft(frac{npi x}{L}right) + b_n sinleft(frac{npi x}{L}right) right] where the coefficients a_0, a_n, and b_n are given by: a_0 = frac{1}{L} int_{-L}^L f(x) dx a_n = frac{1}{L} int_{-L}^L f(x) cosleft(frac{npi x}{L}right) dx b_n = frac{1}{L} int_{-L}^L f(x) sinleft(frac{npi x}{L}right) dx

answer:First, let's find the period of the function. Since the function is defined on the interval [-4, 4], the period is 2L = 8, so L = 4. Now, let's find the coefficients a_0, a_n, and b_n. a_0 = frac{1}{4} int_{-4}^4 f(x) dx = frac{1}{4} left[ int_{-4}^0 1 dx + int_0^4 -1 dx right] = frac{1}{4} left[ (x Big|_{-4}^0) - (x Big|_0^4) right] = frac{1}{4} left[ (0 - (-4)) - (4 - 0) right] = frac{1}{4} left[ 4 - 4 right] = 0 a_n = frac{1}{4} int_{-4}^4 f(x) cosleft(frac{npi x}{4}right) dx = frac{1}{4} left[ int_{-4}^0 1 cdot cosleft(frac{npi x}{4}right) dx + int_0^4 -1 cdot cosleft(frac{npi x}{4}right) dx right] = frac{1}{4} left[ int_{-4}^0 cosleft(frac{npi x}{4}right) dx - int_0^4 cosleft(frac{npi x}{4}right) dx right] Now, integrate the cosine terms: = frac{1}{4} left[ frac{4}{npi} sinleft(frac{npi x}{4}right) Big|_{-4}^0 - frac{4}{npi} sinleft(frac{npi x}{4}right) Big|_0^4 right] = frac{1}{npi} left[ sinleft(frac{npi (0)}{4}right) - sinleft(frac{npi (-4)}{4}right) - sinleft(frac{npi (4)}{4}right) + sinleft(frac{npi (0)}{4}right) right] = frac{1}{npi} left[ - sinleft(npiright) + sinleft(-npiright) right] Since sin(-x) = -sin(x) and sin(nπ) = 0 for all integer values of n, the expression simplifies to: a_n = 0 Now, let's find b_n: b_n = frac{1}{4} int_{-4}^4 f(x) sinleft(frac{npi x}{4}right) dx = frac{1}{4} left[ int_{-4}^0 1 cdot sinleft(frac{npi x}{4}right) dx + int_0^4 -1 cdot sinleft(frac{npi x}{4}right) dx right] = frac{1}{4} left[ int_{-4}^0 sinleft(frac{npi x}{4}right) dx - int_0^4 sinleft(frac{npi x}{4}right) dx right] Now, integrate the sine terms: = frac{1}{4} left[ -frac{4}{npi} cosleft(frac{npi x}{4}right) Big|_{-4}^0 + frac{4}{npi} cosleft(frac{npi x}{4}right) Big|_0^4 right] = frac{1}{npi} left[ cosleft(frac{npi (0)}{4}right) - cosleft(frac{npi (-4)}{4}right) + cosleft(frac{npi (4)}{4}right) - cosleft(frac{npi (0)}{4}right) right] = frac{1}{npi} left[ 1 - cosleft(npiright) + cosleft(npiright) - 1 right] Since cos(nπ) = (-1)^n, the expression simplifies to: b_n = frac{1}{npi} left[ 1 - (-1)^n + (-1)^n - 1 right] = frac{1}{npi} left[ 2 - 2(-1)^n right] Now, we can write the Fourier series for the function f(x): f(x) = frac{a_0}{2} + sum_{n=1}^infty left[ a_n cosleft(frac{npi x}{4}right) + b_n sinleft(frac{npi x}{4}right) right] = 0 + sum_{n=1}^infty left[ 0 cdot cosleft(frac{npi x}{4}right) + frac{1}{npi} left( 2 - 2(-1)^n right) sinleft(frac{npi x}{4}right) right] = sum_{n=1}^infty frac{1}{npi} left( 2 - 2(-1)^n right) sinleft(frac{npi x}{4}right) This is the Fourier series for the given function f(x).

question:A function f(x) has a period of 2 and is defined as follows: f(x) = 1 for -1 < x < 0 and f(x) = -1 for 0 < x < 1 Find the Fourier series of f(x) over the interval [-1, 1].

answer:To find the Fourier series of f(x), we need to determine the coefficients a_n and b_n in the following series representation: f(x) = a_0 + Σ [a_n * cos(nπx) + b_n * sin(nπx)] where the summation is from n = 1 to infinity. First, let's find a_0: a_0 = (1/L) * ∫[f(x)]dx from -L to L, where L is half the period of the function (in this case, L = 1). a_0 = (1/1) * [∫[1]dx from -1 to 0 + ∫[-1]dx from 0 to 1] a_0 = [x] from -1 to 0 + [-x] from 0 to 1 a_0 = (0 - (-1)) + (1 - 0) a_0 = 1 + 1 a_0 = 2 Now, let's find a_n: a_n = (1/L) * ∫[f(x) * cos(nπx)]dx from -L to L a_n = (1/1) * [∫[1 * cos(nπx)]dx from -1 to 0 + ∫[-1 * cos(nπx)]dx from 0 to 1] a_n = [∫[cos(nπx)]dx from -1 to 0 + ∫[-cos(nπx)]dx from 0 to 1] a_n = [sin(nπx)/nπ] from -1 to 0 + [-sin(nπx)/nπ] from 0 to 1 a_n = (0 - sin(-nπ)/nπ) + (-sin(nπ)/nπ - 0) a_n = (sin(nπ)/nπ) - (sin(nπ)/nπ) a_n = 0 Now, let's find b_n: b_n = (1/L) * ∫[f(x) * sin(nπx)]dx from -L to L b_n = (1/1) * [∫[1 * sin(nπx)]dx from -1 to 0 + ∫[-1 * sin(nπx)]dx from 0 to 1] b_n = [∫[sin(nπx)]dx from -1 to 0 + ∫[-sin(nπx)]dx from 0 to 1] b_n = [-cos(nπx)/nπ] from -1 to 0 + [cos(nπx)/nπ] from 0 to 1 b_n = (-cos(0)/nπ - (-cos(-nπ)/nπ)) + (cos(nπ)/nπ - cos(0)/nπ) b_n = (1/nπ - (-1)^n/nπ) + ((-1)^n/nπ - 1/nπ) b_n = 2/nπ (1 - (-1)^n) So, the Fourier series of f(x) is: f(x) = 2 + Σ [2/nπ (1 - (-1)^n) * sin(nπx)] for n = 1 to infinity This is the Fourier series representation of the given function f(x) over the interval [-1, 1].

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