The first term in a Fourier series is the average value (DC value) of the function being approximated. Created by Sal Khan.

In previous lessons we've learned how expansionary monetary policy and expansionary fiscal policy can be used to mitigate a recession, but they don't have to be used in isolation from each other. Often there is simultaneous use of fiscal and monetary policy. Learn what happens when they are used at the same time in this video.

Fiscal policy can be used to close output gaps. Fiscal policy means using either taxes or government spending to stabilize the economy. Expansionary fiscal policy can close recessionary gaps (using either decreased taxes or increased spending) and contractionary fiscal policy can close inflationary gaps (using either increased taxes or decreased spending).

Explore how to think about average fixed, variable, and marginal costs, and how to calculate them, using a firm's production function and costs in this video. Created by Sal Khan.

The fluid mosaic model describes the cell membrane as a tapestry of several types of molecules (phospholipids, cholesterols, and proteins) that are constantly moving. This movement helps the cell membrane maintain its role as a barrier between the inside and outside of the cell environments.

Learn how to calculate interest when interest is compounded continually. We compare the effects of compounding more than annually, building up to interest compounding continually. Created by Sal Khan.

Economists traditionally divide the factors of production into four categories: land, labor, capital, and entrepreneurship. Land refers to natural resources, labor refers to work effort, and capital is anything made that is used to make something else. The last resource, entrepreneurship, refers to the ability to put the other three resources together to create value. In this video, we define each of the four factors of production and provide examples of each.

An introduction to Gravity, Weak, Electromagnetic and Strong Forces. Created by Sal Khan.

The Fourier Series allows us to model any arbitrary periodic signal with a combination of sines and cosines. In this video sequence Sal works out the Fourier Series of a square wave. Created by Sal Khan.

An overview of The Fourteenth Amendment and equal protection.