# Post 120: February 21st, 2017

First order of business today was Algebra. I learned about circles. So, a circle can be described as the set of all points in a plane that are equidistant from a given point on the plane, called the center. Any line segment whose end points are a point of the circle and the circle’s center is a radius of the circle.

Circles also have equations. With center (h, k) and radius r units, the equation is: (x-h)^2 + (y-k)^2 = r^2.

Also, if a line only intersects with only one of the circle’s points is tangent to the circle.

Next up, Economics. I learned about global economic challenges that people face. For example, pollution. Pollution can cause problems down the road, but limiting or preventing it can be expensive and difficult in the short term. Population growth is another issue, as more people means that more production is needed, but resources can be limited. Eventually, a nation may only be able to support so many people with the resources it has.

Lastly, Programming. I learned about series and parallel circuits, which are pretty easy to summarize. A series circuit is a circuit which only has one path for the current to flow through, which are simple, but can have problems. For example, anyone dealing with Christmas tree lights that won’t work, and you need to check every bulb to find out which one is bad.

As for parallel circuits, it’s a circuit that has two or more connections running through it, and different ways for the current to travel. This means that if one part of the circuit fails, the current can still travel.

## Author: Carl Hall

Brick and mortar school, cyber school, and now home school