00:02
Okay, so what is the definition of orthogonal? orthognal matrix is a matrix such that q transpose is equal to q transpose q transpose q is equal to the identity.
00:17
Okay, so they are going to use this definition of orthogonal.
00:32
Okay, so now let's use this.
00:36
So for a, you just have to look at what is qx, and we're going to do it for the squared norm.
00:45
So the squared norm is the same thing as the dot product.
00:49
So it's the same thing as qx transpose qx.
00:54
Okay, because dot product is something transpose the same thing itself.
01:02
So now let's supply the definition of transpose.
01:05
Definition of transpose tells you that's equal to x transpose q transpose q transpose qx.
01:12
And again, this is this...