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numerical analysis
Questions and Answers of
Numerical Analysis
Prove that if xn-1, xn satisfy (19), then xn is the x-intercept of the tangent line to y = f(x) at the point (xn-1, f(xn-1)).
Prove that cos(l) is irrational.
Suppose that f : R → R. If f" exists and is bounded on R, and there is an ε0 > 0 such that |f'(x)| > ε0 for all x ∈ R, prove that there exists a δ > 0 such that if |f(x0)| < δ > 0 for some x0
Let x [0, 1) and an, βn be defined as in Theorem 7.60.a) If f : [0, 1) R and γ R, prove thatb) If f is differentiable at x, prove that
Let x, y, z ∈ Rʹʹ a) If ||x - z|| < 2 and ||y - z|| < 3, prove that ||x - y|| < 5. b) If ||x|| < 2, ||y|| < 3, and ||z|| < 4, prove that |x ∙ y - x ∙ z| < 14. c) If ||x - y|| < 2 and ||z|| <
Prove that the 1-norm and the sup-norm also satisfy Theorem 8.6.
Let B :={x Rn : ||x|| a) If a, b, c B andprove that v belongs to B. b) If a, b B, prove that for all c, d Rn. c) If a, b, c B and n =
Use the proof of Theorem 8.5 to show that equality in the Cauchy-Schwarz Inequality holds if and only if x = 0, y = 0, or x is parallel to y.
Let a and b be nonzero vectors in Rn. a) If ɸ(t) = a + tb for t ∈ R, show that for each to, t0, t1, t2 ∈ R with t1, t2 ≠ t0, the angle between ɸ(t0) - ɸ(t0) - ɸ(t0) and ɸ(t2) - ɸ(t0) is 0
The midpoint of a side of a triangle in R3 is the point that bisects that side (i.e., that divides it into two equal pieces). Let Δ be a triangle in R3 with sides A, B, and C and let L denote the
a) Prove that (1,2,3), (4,5,6), and (0,4,2) are vertices of a right triangle in R3.b) Find all nonzero vectors orthogonal to (1,-1, 0) which lie in the plane z = x.c) Find all nonzero vectors
Let a < b be real numbers. The Cartesian product [a, b] × [a, b] is obviously a square in R2. Define a cube Q in R" to be the n-fold Cartesian product of [a, b] with itself; that is, Q := [a, b] ×
a) Using Postulate 1 in Section 1.2 and Definition 8.1, prove Theorem 8.2.b) Prove Theorem 8.9, parts i) through iii) and vi).c) Prove that if x, y ∈ R3, then ||x × y|| < ||x|| ||y||.
Suppose that {(ak) and are sequences of real numbers which satisfyProve that the infinite series k=1 akbk converges absolutely.
Let a, b, c ∈ R3.a) Prove that if a, b, and c do not all lie on the same line, then an equation of the plane through these points is given by (x, y, z) • d = a • d, whered := (a - b) × (a -
For each of the following functions f, find the matrix representative of a linear transformation T £(R; R'") which satisfiesa) f(x) = (x2, sinx)- b) f(x) = (ex, 3x, l -
Fix T £(R"; RW). Seta) Prove that M1 b) Using the linear property of T, prove that if x 0, then c) Prove that M1 = M2 = ||T||.
a) Find an equation of the hyperplane through the points (1, 0, 0, 0), (2,1, 0, 0), (0,1,1, 0), and (0, 4, 0,1).b) Find an equation of the hyperplane that contains the lines ɸ(t) = (t, t, t, 1) and
Find two lines in R3 which are not parallel but do not intersect.
Suppose that T ∈ £(R"; R'") for some n, m ∈ N.a) Find the matrix representative of T if T(x, y, z, w) = (0, x + y, x - z, x + y + w).b) Find the matrix representative of T if T(x, y, z) = x - y
Suppose that T ∈ £(R"; R'") for some n,m ∈ N. a) If T(l, 1) = (3, π, 0) and T(0, 1) = (4,0, 1), find the matrix representative of T. b) If T(l, I, 0) = (e, π), T(0,-1, 1) = (1, 0), and T(l,
Suppose that a, b, c R3 are three points which do not lie on the same straight line and that U is the plane which contains the points a, b, c. Prove that an equation of II is given by
Recall that the area of a parallelogram with base b and altitude h is given by bh, and the volume of a parallelepiped is given by the area of its base times its altitude. a) Let a, b ∈ R3 be
The distance from a point x0 = (x0, y0, z0) to a plane II in R3 is defined to bewhere v := (x0 - x1, y0 - y1, z0 - z1) for some (x1, y1, z1) II, and v is orthogonal to II (i.e., parallel
a) Prove that ||B(x, y)|| = ||(x, y)|| for all (x, y) ˆˆ R2.b) Let (x, y) ˆˆ R2 be a nonzero vector and φ represent the angle between B(x, y) and (x, y). Prove that cos φ = cos θ.
Sketch each of the following sets. Identify which of the following sets are open, which are closed, and which are neither. Also discuss the connectivity of each set.a) E = {(x, y): y ≠ 0}b) E =
Graph generic open balls in R2 with respect to each of the "non-Euclidean" norms || ∙ ||1 and || ∙ ||∞. What shape are they?
Let n ∈ N, let a ∈ R", let s, r ∈ R with s < r, and setV = {x ∈ R": s < ||x - a|| < r} and E = {x ∈ R" : s < ||x - a|| < r}.Prove that V is open and E is closed.
a) Let a < b and c < d be real numbers. Sketch a graph of the rectangle[a, b] × [c, d] := {(x, y) : x ∈ [a, b], y ∈ [c, d]},and decide whether this set is connected. Explain your
a) Let E1 denote the closed ball centered at (0, 0) of radius 1 and E2 := β√2(2, 0), and sketch a graph of the set U: = {(x, y): x2 + y2 < 1 and x2 - 4x + y2 + 2 < 0}. b) Decide whether U is
Suppose that E ⊂ R" and that C is a subset of E.a) Prove that if E is closed, then C is relatively closed in E if and only if C is (plain old vanilla) closed (in the usual sense).b) Prove that C is
a) If A and B are connected in R" and A ˆ© B ‰ 0, prove that A U B is connected.b) If {Ea}aˆˆA is a collection of connected sets in R" and ˆ©aˆˆAEa ‰ 0, prove thatis
Let V be a subset of R".a) Prove that V is open if and only if there is a collection of open balls {Bα : α ˆˆ A} such thatb) What happens to this result when open is replaced by closed?
Show that if E is closed in R" and a E, then
Find the interior, closure, and boundary of each of the following subsets of R.a) E = {l/n: n ˆˆ N|b)c) E = Uˆžn=1(-n, n)d) E = Q
Let A and B be subsets of Rn.a) Show that ϑ{A ∩ B) ∩ (AC U (ϑB)C) ⊂ 3A.b) Show that if x ∈ ϑ(A ∩ B) and x ∉ (A ∩ ϑB)U(B ∩ ϑA), then x ∈ ϑA∩ϑB.c) Prove that ϑ{A ∩ B) ⊂
Let E ⊂ Rn and U be relatively open in E. a) If ⋃ ⊂ E°, then ⋃ ∩ ϑ⋃ = θ. b) If U ∩ ϑE ≠ 0, then U ∩ ϑU = ⋃ ∩ ϑE.
For each of the following sets, sketch E°, , and ϑE.a) E = {(x, y) : x2 + 4y2 < 1}b) E = {(x, y) : x2 - 2x + y2 = 0} U {(x, 0) : x ∈ [2, 3]}c) E = {(x, y) : y > x2, 0 < y < 1}d) E =
Let E be a subset of R". a) Prove that every subset A ⊂ E contains a set B which is the largest subset of A that is relatively open in E. b) Prove that every subset A ⊂ E is contained in a set B
Complete the proof of Theorem 8.36 by verifying (10).
Prove that if E ⊂ R is connected, then E° is also connected. Show that this is false if "R" is replaced by "R2."
Suppose that E ⊂ R" is connected and that E ⊂ A ⊂ . Prove that A is connected.
A set A is called clopen if and only if it is both open and closed.a) Prove that every Euclidean space has at least two clopen sets.b) Prove that a proper subset E of Rn is connected if and only if
Show that Theorem 8.37 is best possible in the following sense.a) There exist sets A, B in R such that (A U B)° ± A° ‹ƒ B".c) There exist sets A, B in R such that Ï‘(A U B) ‰ Ï‘A
Using Definition 9.1i, prove that the following limits exist,a)b) c)
Using limit theorems, find the limit of each of the following vector sequences.a)b) c)
Suppose that xk → 0 in Rn as k → ∞ and that yk is bounded in Rn.a) Prove that xk ∙ yk → ■ 0 as k ∞.b) If n = 3, prove that x* x y* -> 0 as A: -> oo.
Suppose that a ∈ Rn, that xk → a, and that xk - yk → 0, as k → ∞. Prove that yk → a as k → ∞.
a) Prove Theorem 9.4i and ii. b) Prove Theorem 9.4iii and iv. c) Prove Theorem 9.4v. d) Prove Theorem 9.6.
Let E be a nonempty subset of Rn.a) Show that a sequence xk ∈ E converges to some point a ∈ E if and only if for every set U, which is relatively open in E and contains a, there is an N ∈ N
a) A subset E of Rn is said to be sequentially compact if and only if every sequence xk ∈ E has a convergent subsequence whose limit belongs to E. Prove that every closed ball in Rn is sequentially
a) Let E be a subset of Rn. A point a ∈ Rn is called a cluster point of E if E ∩ Br (a) contains infinitely many points for every r > 0. Prove that a is a cluster point of E if and only if for
Suppose that E is a bounded noncompact subset of Rn and that f: E (0, ). If there is a g: E R such that g(x) > f(x) for all x E, then
Suppose that £ is a compact subset of R. If for every x ∈ E there exist a nonnegative function f = fx and an r = r(x) > 0 such that f is C∞ on R, f(t) = 1 for t ∈ (x - r, x + r), and f(t) = 0
Suppose that K is compact in Rn and that for every x ∈ K there is an r = r(x) > 0 such that Br(x) ∩ K = {x}. Prove that K is a finite set.
Let E be closed and bounded in R, and suppose that for each x ∈ E there is a function fx, nonnegative, nonconstant, increasing, and C∞ on R, such that fx(x) > 0 and fʹx(y) = 0 for y ∉ E. Prove
Suppose that f: Rn → Rn and that a ∈ K, where K is a compact, connected subset of Rn. Suppose further that for each x ∈ K there is a δx > 0 such that f(x) = f(y) for all y ∈ Bδx(x). Prove
Define the distance between two nonempty subsets A and B of R" bya) Prove that if A and B are compact sets which satisfy A ˆ© B = θ, then dist(A, B) > 0.b) Show that there exist nonempty,
Suppose that E and V are subsets of R with E bounded, V open, and ⊂ V. Prove that there is a C∞ function F: E → R such that F(x) > 0 for x ∈ E and f(x) = 0 for ∉ V.
For each of the following functions, find the maximal domain of f, prove that the limit of f exists as (x, y) (a, b), and find the value of that limit. (You can prove that the limit
Compute the iterated limits at (0, 0) of each of the following functions. Determine which of these functions has a limit as (x, y) (0, 0) in R2, and prove that the limit exists.a)b) c)
Prove that each of the following functions has a limit as (x, y) (0, 0).a)b) where a is ANY positive number.
A polynomial on Rn of degree N is a function of the formwhere aj1 jn are scalars, N1,..., Nn are nonnegative integers, and N = N1 + N2 +
Suppose that a ∈ Rn that L ∈ Rm, and that f: Rn → Rm. Prove that if f(x) → L as x → a, then there is an open set V containing a and a constant M > 0 such that ||f(x)|| < M for all x ∈ V.
Suppose that a = (a1 ∙ ∙ ∙ an) ∈ Rn, that fj: R → R for j = 1, 2,..., n, and that g(x1, x2,..., xn) := f1(x1) ∙ ∙ ∙ fn(xn).a) Prove that if fj(t) fj(a) as t → aj, for each j =
Suppose that g : R → R is differentiable and that g'(x) > 1 for all x ∈ R. Prove that if g(l) = 0 and f(x, y) = (x - l)2(y + l)/(yg(x)), then there is an L ∈ R such that f(x, y) → L as (x, y)
Define f and g on R by f(x) = sin x and g(x) = x/|x| if x ≠ 0 and g(0) = 0.a) Find f(E) and g(E) for E = (0, π), E = [0, π], E = (-1, 1), and E = [-1, 1]. Compare your answers with what Theorems
a) A set E ⊂ Rn is said to be polygonally connected if and only if any two points a, b ∈ E can be connected by a polygonal path in E; that is, there exist points xk ∈ E, k = 1,. . . . . N, such
Define f on [0, ∞) and g on R by f(x) = √x and g(x) = 1/x if x ≠ 0 and g(0) = 0.a) Find f(E) and g(E) for E = (0, 1), E = [0, 1), and E = [0, 1]. Compare your answers with what Theorems 9.26,
Suppose that A is open in Rn and f: A → Rm. Prove that f is continuous on A if and only if f-l (V) is open in Rn for every open subset V of Rm.
Suppose that A is closed in Rn and f: A → Rm. Prove that f is continuous on A if and only if f-l (E) is closed in Rn for every closed subset E of Rm.
Suppose that E ⊂ Rn and that f: E → Rm. a) Prove that f is continuous on E if and only if f-1(B) is relatively closed in E for every closed subset B of Rm. b) Suppose that f is continuous on E.
Prove thatis continuous on R2.
Let H be a nonempty, closed, bounded subset of Rn.a) Suppose that f : H Rm is continuous. Prove thatis finite and there exists an x0 H such that ||f(x0)|| = ||f||H. b) A
Let E ⊂ Rn and suppose that D is dense in E (i.e., that D ⊂ E and = E). If f: D → Rm is uniformly continuous on D, prove that f has a continuous extension to E; that is, prove that there is a
Let E be a connected subset of Rn. If f : E → R is continuous, f(a) ≠ f(b) for some a, b ∈ E, and y is a number which lies between f(a) and f(b), then prove that there is an x ∈ E such that
Identify which of the following sets are compact and which are not. If E is not compact, find the smallest compact set H (if there is one) such that E ⊂ H.a) [1/k : k ∈ N} U {0}b) {(x, y) ∈ R2
Let A, B be compact subsets of Rn. Using only Definition 9.10ii, prove that AU B and A ∩ B are compact.
Suppose that E ⊂ R is compact and nonempty. Prove that sup E, inf E ∈ E.
Suppose that {Va}a∈A is a collection of nonempty open sets in Rn which satisfies Va ∩ Vβ = θ for all α ≠ β in A. Prove that A is countable. What happens to this result when open is omitted?
Prove that if V is open in Rn, then there are open balls B1, B2,..., such thatProve that every open set in R is a countable union of open intervals.
Let n ∈ N.a) A subset E of Rn is said to be sequentially compact if and only if every sequence in E has a convergent subsequence. whose limit belongs to E. Prove that every compact set is
Let H ⊂ Rn. Prove that H is compact if and only if every cover {Ea}a∈A of H, where the Eα's are relatively open in H, has a finite subcovering.
Suppose that f, fk: R → R are continuous and nonnegative. Prove that if f(x) → 0 as x → ±∞ and fk ↑ f everywhere on R, then fk → f uniformly on R.
For each of the following functions, find a formula for Ïf(t).a)b) c)
Prove that (1 - x/k)k → e-x uniformly on any closed, bounded subset of R.
Show that if f: [a, b] → R is integrable and g: f([a, b]) → R is continuous, then g o f is integrable on [a, b]. (Notice by Remark 3.34 that this result is false if g is allowed even one point of
Using Theorem 7.10 or Theorem 9.30, prove that each of the following limits exists. Find a value for the limit in each case.a)b) where f is continuously differentiable on [0, 1] and f'(0) > 0. c) d)
a) Prove that for every ε > 0 there is a sequence of open intervals {Ik}kˆˆN which covers [0, 1] ˆ© Q such thatb) Prove that if {Ik}kˆˆN is a sequence of open intervals which covers [0,
Let E1 be the unit interval [0, 1] with its middle third (1/3, 2/3) removed (i.e., E1 = [0, l/3]U[2/3, 1]). Let E2 be E1 with its middle thirds removed; that is,E2 = [0, 1/9] U [2/9, 1/31 U [2/3,
a) A subset E of X is said to be sequentially compact if and only if every sequence xn ∈ E has a convergent subsequence whose limit belongs to E. Prove that every sequentially compact set is closed
Prove that {xk} is bounded in X if and only if supk∈N p(xk, a) < ∞ for all a ∈ X.
Let Rn be endowed with the usual metric and suppose that {xk} is a sequence in R" with components xk(j); that is,a) Use Remark 8.7 to prove that {xk} is bounded in Rn if and only if there is a C >
a) Let a ∈ X. Prove that if xn = a for every n ∈ N, then xn converges. What does it converge to?b) Let X = R with the discrete metric. Prove that xn → a as n → ∞ if and only if xn = a for
a) Let [xn) and {yn} be sequences in X which converge to the same point. Prove that p(xn yn) → 0 as n → ∞. b) Show that the converse of part a) is false.
Let (xn) be Cauchy in X. Prove that {xn} converges if and only if at least one of its subsequences converges.
Prove that the discrete space R is complete.
a) Prove that the metric space C[a, b] in Example 10.6 is complete. b) Let ||f||1: = ∫ba |f(x)|dx and define dist(f, g) := ||f - g||1 for each pair f, g ∈ C[a, b]. Prove that this distance
a) Show that if x ∈ Br(a), then there is an ∈ > 0 such that the closed ball centered at x of radius ε is a subset of Br{a).b) If a ≠ b are distinct points in X, prove that there is an r
Find all cluster points of each of the following sets.a) E = R\Qb) E = [a, b), a, b ∈ R, a < bc) E = {(-1)nn : n ∈ N}d) E = {xn : n ∈ N}, where xn → x as n → ∞e) E = {l, 1, 2, 1, 2, 3,
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