00:02
In this question we have been given that x is a complex hilbert space.
00:10
This is what we have been given and it is given with the inner product and a norm.
00:17
We need to find, let's prove 2a first.
00:21
So we have to prove that p is orthogonal projection, orthogonal projection operator, okay? projection operator if and only if p square is equal to p and p and p star is equal to p correct so this is what we need to prove and let us see how can we do this so we first prove the forward direction correct so we consider that p is an orthogonal projection then then what we can say that p of x is going to lie inside r p that we know and in that case i minus p times of x it lies in np also one thing we should remember that r p and n p both are perpendicular it is perpendicular to n p this thing we should know correct so now if i consider what is my p square of x so this is p of px and this is p of px is just equal to px since it is a projection operator so i'm using that property to direct write these things okay so this is true for every x belonging to x okay so we assume some two element in x then what i will do i will consider the inner product of px with y so this can also be written as px here i will add and subtract p y correct so just i have added and subtracted so if we saw what i'm going to get px comma p y plus inner product px comma y minus p y correct this belongs to rp and this belongs to np and we know that rp and np both are perpendicular so this inner product will be zero so this is something px py plus zero so this i am getting equal to px py it was px comma y correct let's call this as equation one similarly, similarly, what i can say, the next thing, if i am taking x with p y, i will apply the same condition and prove that this is equal to px, p y, correct inner product.
03:13
Let's say this is our equation number 2.
03:16
So what i can say from 1 and 2 or i can say hence from 1.
03:26
1 and 2 what i have observed let me write that so pxy is equal to px y and this is equals to x comma p y okay so this was our observation that we did now we have to move forward and let's see what we can do so then what i will get p x comma y which will equal to x comma p y.
04:02
So this will imply that p is self adjoint, self adjoint.
04:11
So this will imply that p star will be equal to p.
04:15
So this is what we needed to prove.
04:18
Correct.
04:19
And now let's move to the another part.
04:25
Now we show that for, okay, so converse part...