Last night I worked through a unit in Khan Academy to learn about composite functions and invertible functions.

This morning, I moved on to the next unit: trigonometry.

This is really important for me to understand because trigonometric functions are root of analyzing and processing signals.

After going through the first lesson in trigonometry, the fundamentals of the sin, cos, and tan functions are very simple.

They are functions that take an angle (or radian) as an input, and they output the length of a side of the parent triangle.

This fits into signal processing because the (x,y) values of sinusoidal waves oscillate between 1 and -1. Which can be mapped to values in the unit circle.

I didn't write this clearly or eloquently. But that's okay. Just repeating what I learned this morning. And, here's a bit more repetition:

cos 𝛑/3 = 1/2

sin 𝛑/3 = √3/2

cos 𝛑/6 = √3/2

sin 𝛑/6 = 1/2

cos 𝛑/4 = √2/2

sin 𝛑/4 = √2/2