updates
Sine wave with increasing frequencies in Matlab
In my opinion, the following code should produce a sine wave that has a frequency of $2\text{Hz}$ at $t=20$, but when I count the periods between $t=19$ a...
Apr 16, 2026
Archive: Updates
updates
Indefinite integral with product rule
Assume the following integral: $$\int \sin x \cos x\ \ dx $$ My understanding now is, that I can choose both for $f(x)$ and $g'(x)$ respectively, lea...
Apr 15, 2026
updates
Formerly good at math, but after 12 years I've lost most of my skills. Now I need them once again. Any advice to grow them back?
I love math, and I used to be very good at it. The correct answers came fast and intuitively. I never studied, and redid the demonstration live for the te...
Apr 15, 2026
updates
Understanding the Hopf Link
I am trying to understand why the preimages of two points under the Hopf fibration are linked. I thought that two circles in $\mathbb{C}^n$ are linked iff...
Apr 15, 2026
updates
How many numbers between 1 and 1000 can be divided by both $a$ and $b$
I need to find the number of natural numbers between 1 and 1000 that are divisible by 3, 5 or 7. I know that given a set of numbers, 1 ... n, the number o...
Apr 15, 2026
updates
Calculate specified probability
Question: Suppose that $T$ is a random variable. Given that $P(-3.3 \leq T \leq 3.3) =.775$, and that $P(T<-3.3)=P(T > 3.3)$, we are to find $P(T &l...
Apr 15, 2026
![Prove A or (A and B) is equivalent to A [duplicate]](https://news.conceivablytech.com/uploads/prove-a-or-a-and-b-is-equivalent-to-a-duplicate_720.jpg)
updates
Prove A or (A and B) is equivalent to A [duplicate]
Prove $A \lor (A \land B) \Leftrightarrow A$ without using truth table. The proof may involve expanding $B$ into $B \land B$ or possibly $B \lor B$. I am ...
Apr 15, 2026
updates
Probability question (Birthday problem)
I was wondering if someone could critique my argument here. The problem is to find the probability where exactly 2 people in a room full of 23 people shar...
Apr 15, 2026
updates
Limit Properties In Calculus
I am currently learning about limits in Khan academy. I've attached a screenshot below on the section that confuses me: What confuses me is 3 things:...
Apr 15, 2026
updates
What is $\;\int xe^{-x^2} \,dx\;?$
What is $$\int xe^{-x^2} dx\quad?$$ I used substitution to rewrite it as $$\int -\dfrac{1}{2}e^u\, du$$ but this is too hard for me to evaluate. When I us...
Apr 15, 2026
