Reputation
20,805
Top tag
Next privilege 25,000 Rep.
Access to site analytics
Badges
5 29 67
Newest
 calculus
Impact
~101k people reached

7h
answered Prove that $\frac{1}{n+1} + \frac{1}{n+3}+\cdots+\frac{1}{3n-1}>\frac{1}{2}$
9h
comment Meaning of $\partial f /\partial x$
Yes, that's right......
10h
answered Meaning of $\partial f /\partial x$
Jan
31
revised Complex number ( prove )
added 160 characters in body
Jan
31
comment Differential equations stuck
Downvoter should expain
Jan
31
answered Complex number ( prove )
Jan
29
comment What comes first here? pemdas doesnt really tell me what to do here
@RossMillikan You're quite right. I misspoke
Jan
29
comment What comes first here? pemdas doesnt really tell me what to do here
Because multiplication is commutative, it doesn't matter in which order you multiply out the terms. I suggest trying both ways and then learning from that which you find the more elegant.
Jan
26
comment Is the set $\{x \in \mathbb{R}^3 : |x_1-2| + |x_2-1| \leq 2\}$ compact?
No, that's incorrect. In $\mathbb R^n$ under the usual topology, a subset $U$ is compact iff it is bounded and closed. $C \times \mathbb R$ is not bounded.
Jan
26
answered Is the set $\{x \in \mathbb{R}^3 : |x_1-2| + |x_2-1| \leq 2\}$ compact?
Jan
26
comment Calculus: Integration problem.
Yes, see edits above
Jan
26
revised Calculus: Integration problem.
added 191 characters in body
Jan
26
comment Calculus: Integration problem.
Good. Custom on this site is to upvote and/or accept an answer that addresses your question.
Jan
26
revised Calculus: Integration problem.
deleted 8 characters in body
Jan
26
comment Calculus: Integration problem.
Then let me know if the answer is not clear. I'll just add that $$\lim_{t\to\infty} \int_1^t \frac{dx}{x} = \lim_{t\to\infty} \log t$$ in the sense that both limits diverge to positive $\infty$
Jan
26
comment Calculus: Integration problem.
I am trying to clarify your question (and giving answers to two possible versions). What exactly is it you are asking? Is it either of the versions I have given, or something else?
Jan
25
answered Calculus: Integration problem.
Jan
25
comment Calculus: Integration problem.
Do you mean: for a particular $t > 0$, does there exist a function $f$ which is not the function $x \mapsto 1/x$ such that $$\int_1^\infty f(x) \ dx = \log t$$ Or do you mean something else?
Jan
24
comment How many terms in arithmetic series where sum < 1000?
Write down the sum for $n$ terms and then solve for $n$, remembering to find the integer part
Jan
19
answered Prove that if $ax^2 + bx + c = 0$ for all values of $x$, then $a=b=c=0$