Uploaded June 2016 | Updated September 2026, 2 weeks ago
In this video I go through the proof for the angle difference identities for both sine and cosine. We will need to know the angle sum identities, so if you want a proof of those, watch this video:
goo.gl/Uzp7bM
In this video I go through the proof for the angle difference identities for both sine and cosine. We will need to know the angle sum identities, so if you want a proof of those, watch this video:
goo.gl/Uzp7bM
![Explained: Airfoil Chord [Airplanes]](https://i.ytimg.com/vi/Eh5W61iswSY/mqdefault.jpg "Explained: Airfoil Chord [Airplanes]
The airfoil chord is a vital part of understanding the angle of attack of an airfoil, as well as other aerodynamic parameters in aircraft design. The definition of the chord line is straightforward, while the definition for the leading edge (LE)/trailing edge (TE) are a little more ambiguous.
Second of All Comment
The first of all comment (that I made in the video) was that the angle of attack actually changes based off of where you define the leading edge to be. The comment I forget to say in the video is that the chord length also changes based on the LE location. For the minimum x value LE, the chord line is longer than the minimum radius of curvature LE.")
![Explained: Angle of Attack [Airplanes]](https://i.ytimg.com/vi/Fm2Az-PgPUU/mqdefault.jpg "Explained: Angle of Attack [Airplanes]
The angle of attack (AoA) is one of the most important parameters when studying how planes fly. By definition, it is the angle between some reference line of the plane (in our case the chord line of the wing) and the relative wind. The AoA will be vital when talking about lift curves and how wings generate lift.
Chord Line: http://www.youtube.com/watch?v=Eh5W61iswSY")
