In: Advanced Math
V is a subspace of inner-product space R3, generated by vector
u =[1 1 2]T and v =[ 2 2 3]T.
T is transpose
(1) Find its orthogonal complement space V┴ ;
(2) Find the dimension of space W = V+ V┴;
(3) Find the angle q between u and v; also the angle b between u and normalized x with respect to its 2-norm.
(4) Considering v’ = av, a is a scaler, show the angle q’ between u and v’
Problem (1)
Note that and
are non-zero vectors
and one is not a scalar multiple of another.
SInce ,
so,
This is a side
remark if you know that
Then,
i.e., the orthogonal complement of is one dimensional.
So, any non zero vector in is a
basis of
Continuing back to our problem
Let
So, it is orthogonal to every vector in , in particular to
and
,
i.e.,
Putting this in equation , we obtain
.
This in fact proves that is one
dimensional as we claimed above.
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Problem (2)
By definition,
Now, by dimension formula, we obtain
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Problem (3)
Let
be the angle between
and
.
Now, we know that
Now, the problem does not mention what is.
Now, if is mistakenly typed
, then
the angle does not change whether you scale it by a positive
constant.
So, the answer still remains the same.
So, I am assuming that is the unit vector
spanning
. If
there is any confusion, please mention it in the comments so that I
can correct myself. Thank you. I will proceed with this.
i.e.,
Let
be the angle between
and
.
Now, we know that
But
since
and
.
since
are non-zero
vectors
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Problem (4)
Let
If , then
, but
it does not make sense to talk about angle between zero vector and
.
So, assume that is non-zero.
Let be the angle between
and
.
Now, again we have,
since
are non-zero
vectors
Case (1):
Then
since
Case (2):
Then
since
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