Suppose (X, dX) and (Y, dY ) are metric spaces. Define d : (X ×Y
)×(X × Y ) → R by d((x, y),(a, b)) = dX(x, a) + dY (y, b). Prove d
is a metric on X × Y .
Let (X,dX),(Y,dY ) be metric spaces and f: X → Y be a continuous
bijection. Prove that if (X, dX ) is compact, then f is a
homeomorphism. (Hint: it might be convenient to use that a function
is continuous if and only if the inverse image of every open set is
open, if and only if the inverse image of every closed set is
closed).
d^2y/dx^2 − dy/dx − 3/4 y = 0,
y(0) = 1, dy/dx(0) = 0,
Convert the initial value problem into a set of two coupled
first-order initial value problems
and find the exact solution to the differential equatiion
Euclidean metric) The metric
d
((
x
1
,x
2
)
,
(
y
1
,y
2
)) =
√
(
x
1
−
x
2
)
2
+ (
y
1
−
y
2
)
2
on
R
2
generates the standard (product) topology on
R
2
.