00:03
In this question, we are given a line represented by these parametric equations, and we are asked to do two things.
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A.
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Find a basis for this subspace.
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And b.
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Find a standard matrix for the projection onto that subspace, that line.
00:29
So, without further ado, let's get started.
00:32
For part a, we want to find a basis, that is, a set of vectors such that all possible linear combinations of those vectors will cover the subspace.
01:00
So in other words, find a set of vectors such that any point on this line will be able to be written as a linear combination of those vectors.
01:12
So in this case, we know that each of x, y, and z is represented as a multiple of t.
01:24
So we know the vector of unknowns, x, y, z, is a linear combination, that is, a scalar multiple of the single vector 2, negative 1, 4.
01:47
Since x is 2t, y is minus t, and z is 4t, x, y, z is just t times the vector 2, minus 1, 4.
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So our basis is just the single vector 2, minus 1, 4.
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Now for part b, we want to find the standard matrix for the orthogonal projection onto this subspace.
02:23
For that, recall that we have a formula for the standard matrix of orthogonal projections onto column spaces of matrices...