00:01
So we have two vectors with the same magnitude.
00:04
We're trying to show that there's sum, u plus v, dotted with u minus v, is zero, because they're orthogonal.
00:13
So let u equal vector a1, b1, and v is vector a2, b2.
00:20
So the magnitude of u is the square root of a1 squared plus b1 squared, and the magnitude of v is a2 squared plus b2 squared.
00:31
Since the magnitudes are equal, the square of their magnitudes are also equal.
00:37
So if i square u's magnitude, i get a1 squared plus b1 squared.
00:42
And if i take v's magnitude and square it, i get a2 squared plus b2 squared.
00:48
So this right here is all of the kind of givens.
00:53
Now let's actually do u plus v dotted with u minus v.
00:58
Vector u plus v would be the a1 plus a two the two x components added and then b1 plus b2 is the two y components added and then u minus v is the x component minus the other x component and then b1 minus b2 so let's do the dot product so that's going to do a 1 plus a 2 times a 1 minus a 2 plus we're going to do b1 plus b2 times b1 minus b2 you should recognize that if you foil this it's a 1 and a 1 and a 2 same components with a plus and a minus it's a difference of square pattern so it's going to be a 1 squared minus a 2 squared if you do foil, you'll get that.
02:02
And then same thing over here with our bs.
02:05
We're going to do b1...