Categories
Algebra 1 Algebra 2 Math Math Analysis Pre-Calculus

From Low to High with Absolute Value

For those of you who know how to solve absolute value inequalities, here is how they also mean something like “numbers between 8 and 14.”

Categories
Math Physics Pre-Calculus Proofs Proving Identities Science Trigonometry

Spin One Particle Rotates Like a Vector, y-axis

In The Feynman Lectures on Physics, Volume 3 Chapter 5, Feynman poses a challenge to the reader: show that a particular combination of plus, minus and zero states of a spin one particle transforms under a rotation just like a vector does. In this previous video I reviewed the details of proving it for rotations around the z-axis. Here I go over the more complicated proof for rotations around the y-axis.

Categories
Complex Numbers Math Physics Pre-Calculus Proofs Proving Identities Science Trigonometry

Spin One Particle Rotates Like a Vector, z-axis

In The Feynman Lectures on Physics, Volume 3 Chapter 5, Feynman poses a challenge to the reader: show that a particular combination of plus, minus and zero states of a spin one particle transforms under a rotation just like a vector does. Here I go over how to work that problem using only what was covered in the book up to that point.

Categories
Calculus Differential Equations Physics Science

Physics Pendulum Problem

Getting the Period of a Spring-Operated Physical Pendulum

A juicy physics problem that requires delving into the differential equation for pendulum motion. A rod of mass M on a pivot a distance r from the end is driven by a spring of constant k pulling the end back and forth to make an (admittedly stupid) physical pendulum. We have to show that its period T is given by T^2 = 4\pi \frac{M}{3kr^2} (L^2 + 3r^2 -3rl) .

Categories
Physics Science

A Rock on the Moon

A Flying Rock on the Moon — a Kinematics Problem

A nice tough physics kinematics problem: how high will a flying rock on the moon rise if all you know is how long it took to pass a viewport?

Categories
Math Math Analysis Pre-Calculus Proofs Proving Identities Trigonometry

Another Trig Identity

A moderately difficult trig identity: prove \frac{ \frac{1}{tan(x)}+cot(x) }{ \frac{1}{tan(x)}+tan(x) }= \frac{2}{sec^2(x)} using u-substitution.

Categories
Calculus integrals Math

Integrate a Rational Expression

This video walks through doing \int \frac{x^3}{1+x^4}\,dx using u-substitution.

Categories
Geometry Math

A Geometry Proof

Prove 2 lines parallel using CPCTC

Geometry proofs don’t have to be nightmares. You can create your chain of logic just right if you start at the END. I’ll show you what I mean…

Categories
Calculus Line Integrals Math Multivariable Calculus Vector Calculus

Find Potential Function Using Partial Integration

Once you’ve established that curl F = 0, you know that F is the gradient of some potential ⱷ. You can use the Fundamental Theorem to evaluate ∫F.dr — if only you could find the potential function. In this video I go over a straighforward method of finding the potential function using partial integration. (Note: the sound quality gets wonky near the end but you can still hear what I’m explaining perfectly well. Apologies and I’ll figure out eventually why that happens.)

Categories
Geometry Math Trigonometry

Area of Octagon Given Side Length

A step-by-step example of how to find the area of a polygon