Homework Assignment 4
Limits
Please submit the answers to the following in electronic
format, either TeX, Word or PDF.
(Be as rigorous and precise as you can!)
- Show that limx → 0 sin(x)/x = 1, using the
ε-Δ proof.
[Hint]
- Using the result of the previous problem,
show that limx → 0 sin(sin(x))/x exists
[Hint]
- Show that limx → 0 sin(1/x) does not
exist using the ε-Δ proof.
[Hint]
- Show that as x → ∞ [√(x+1)-√(x)] = 0
[Hint]
- Show that the Fibonacci sequence of numbers 1,1,2,3,5,8,13,
given by the relationship an+1=an+an-1
satisfies
[Hint]
Given this recursion relation, find the asymptotic limit of an
as n → ∞. This means find a c and an r such that
limn → ∞ an/(crn) = 1
- Show that one can compute π by the infinite series
π = 4*(1-1/3+1/5-1/7+1/9-1/11+1/13-1/15+1/17-...)
=∑0 ∞ (-1)n
1/(2n+1)
that is from the sum of the alternating series of reciprocals of odd
numbers.
[Hint]
Extra Credit; Derive as many of the
series representations for Pi as you can. There are 43 of them
listed in this reference!
- Show that the non-alternating
series ∑n=1n=∞ 1/(2n+1)
diverges, that is, becomes infinite.
[Hint]
- In the section "Archimedes the Numerical Analyst" in the reference
Archimedes
There is a procedure to calculate π to 18 decimal places strictly
from inscribed and circumscribed regular polygons of 3, 6, 12, 24, 48, and 96
sides respectively. Carry out this procedure, steps 1-7, or this
reference and show that it is correct.
See this
reference (Section 1.3) for the correct relationship
[Hint]
- Define the Heaviside function as
H(t) = 0 if t < 0,
and
H(t) = 1 if t >= 0
Show, using an ε-Δ proof that the limit of H(t) as
t → 0 does not exist.
[Hint]
- Show that
lim x → 0+ xx = 1
lim x → 0+ means that x approaches zero, but only takes
on positive values...
[Hint]