Instructional Video
Khan Academy

Khan Academy: Orthogonal Projections: Projection Is Closest Vector in Subspace

9th - 10th
A video lesson proving that the projection of a vector is actually the closest vector in the subspace to the original vector.
Instructional Video
Khan Academy

Khan Academy: A Projection Onto a Subspace Is a Linear Transforma

9th - 10th
A video lesson proving that any projection onto a subspace is actually a linear transformation. It includes a brief description of how the results can be useful in 3-D graphical programming.
Instructional Video
Khan Academy

Khan Academy: Orthogonal Projections: Least Squares Approximation

9th - 10th
A video lesson explaining the least squares approximation for otherwise unsolvable matrix equations. Presents the motivation for why the least squares approximation is useful. Derives the formula for finding the least squares approximation.
Instructional Video
Khan Academy

Khan Academy: Orthogonal Projections: Another Least Squares Example

9th - 10th
This is a video lesson on using the least squares approximation to find the line of best fit for a set of points. Includes a concrete example dealing with a set of 4 points.
Instructional Video
Khan Academy

Khan Academy: Orthogonal Projections: Subspace Projection Matrix Example

9th - 10th
This video uses a concrete example for how to find the projection of an arbitrary vector onto a specific subspace in R4. Uses a 4 x 2 basis matrix for the subspace.
Instructional Video
Khan Academy

Khan Academy: Orthogonal Projections: Visualizing a Projection Onto a Plane

9th - 10th
A video lesson showing what a projection onto a plane could look like. Illustrates that the newly derived definition of a projection holds true for projections onto subspaces other than lines.
Instructional Video
Khan Academy

Khan Academy: Orthogonal Projections: Another Example of a Projection Matrix

9th - 10th
A video lesson figuring out the transformation matrix for a projection onto a subspace by figuring out the matrix for the projection onto the subspace's orthogonal complement first.