Let X be a compact space and let Y be a Hausdorff space. Let f ∶...
Let X be a compact space and let Y be a Hausdorff space. Let f ∶
X → Y be continuous. Show that the image of any closed set in X
under f must also be closed in Y .
Solutions
Expert Solution
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Problem 16.8 Let X and Y be compact metric spaces and let f: X →
Y be a continuous onto map with the property that
f-1[{y}] is connected for every y∈Y. Show that ifY is
connected then so isX.
The curried version of let f (x,y,z) = (x,(y,z)) is
let f (x,(y,z)) = (x,(y,z))
Just f (because f is already curried)
let f x y z = (x,(y,z))
let f x y z = x (y z)
Let V be a Hilbert space. Let f(x) = ∥x∥ for x ∈ V. Using the
definition of Frechet differentiation, show that ∇f(x) = x for all
x ̸= 0. Furthermore, show that f(x) is not Frechet differentiable
at x = 0.
5. Let X, Y and Z be sets. Let f : X ! Y and g : Y ! Z
functions.
(a) (3 Pts.) Show that if g f is an injective function, then f
is an injective function.
(b) (2 Pts.) Find examples of sets X, Y and Z and functions f
: X ! Y and g : Y ! Z such that g f is
injective but g is not injective.
(c) (3 Pts.) Show that if...
Let f(x, y) = − cos(x + y2
) and let a be the point a = ( π/2,
0).
(a) Find the direction in which f
increases most quickly at the point
a.
(b) Find the directional derivative
Duf(a) of f at
a in the direction u = (−5/13 , 12/13)
.
(c) Use Taylor’s formula to calculate a quadratic approximation
to f at a.
Let f (x, y) = c, 0 ≤ y ≤ 4, y ≤ x ≤ y + 1, be the
joint pdf of X and Y.
(a) (3 pts) Find c and sketch the region for which f (x, y) >
0.
(b) (3 pts) Find fX(x), the marginal pdf of X.
(c) (3 pts) Find fY(y), the marginal pdf of Y.
(d) (3 pts) Find P(X ≤ 3 − Y).
(e) (4 pts) E(X) and Var(X).
(f) (4 pts) E(Y)...
Let f ( x , y ) = x^ 2 + y ^3 + sin ( x ^2 + y ^3 ). Determine
the line integral of f ( x , y ) with respect to arc length over
the unit circle centered at the origin (0, 0).
Let f(x,y) be a scalar function, and let F(x,y,z) be a vector
field. Only one of the following expressions is meaningful. Which
one?
a) grad f x div F
b) div(curl(grad f))
c) div(div F)
d) curl(div(grad f))
e) grad(curl F)
2 Let F be a field and let R = F[x, y] be the ring of
polynomials in two variables with coefficients in F.
(a) Prove that
ev(0,0) : F[x, y] → F
p(x, y) → p(0, 0)
is a surjective ring homomorphism.
(b) Prove that ker ev(0,0) is equal to the ideal (x, y) = {xr(x,
y) + ys(x, y) | r,s ∈ F[x, y]}
(c) Use the first isomorphism theorem to prove that (x, y) ⊆
F[x, y]...