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"e^(-jwt) decreases with increasing t"?

A

Airy R. Bean

Jan 1, 1970
0
If the sentiment expressed in the thread title were to
be expressed by someone with two degrees, one in
electronics and the other in mathematics, someone who
holds a position of authority in the training of electrical
engineering newcomers, what would such a statement say
about the state of engineering education today? (Especially
when that statement had been made in response to the
identity, "cos(wt) = 1/2 * ( e^(jwt) + e^(-jwt) )2 such that
the context was clear?)
 
D

daestrom

Jan 1, 1970
0
Airy R. Bean said:
If the sentiment expressed in the thread title were to
be expressed by someone with two degrees, one in
electronics and the other in mathematics, someone who
holds a position of authority in the training of electrical
engineering newcomers, what would such a statement say
about the state of engineering education today? (Especially
when that statement had been made in response to the
identity, "cos(wt) = 1/2 * ( e^(jwt) + e^(-jwt) )2 such that
the context was clear?)

Clearly, the quantity 'e^(-jwt)' does in fact decrease as 't' moves in the
positive direction (i.e. increases) if 'w' is constant and 't' and 'w' are
limited to the domain of real numbers (not imaginary). To suggest otherwise
is foolish. To read more into the quantity 'e^(-jwt)' than is there, is
equally foolish.

To try and make some philosophical attack about the education of someone
based on that statement, only shows that you seem to think it does not
'decrease with increasing t'. Obviously you have an interpretation of
mathematics and English that is in the minority.

The context of where the expression is used is immaterial. Notice that a
corollary is also true, the term 'e^(-jwt)' increases with decreasing 't'
(again, if 'w' is constant and 't' and 'w' are limited to the domain of real
numbers).

The term could be in *any* formula, and the statement that the term
'e^(-jwt) decreases with increasing t' (provided 'w' is constant and 't' and
'w' are limited to the real domain) would still be the only rational
position to take.

daestrom
P.S. And I don't know of any application where the frequency ('w') or time
('t') are *not* limited to the real domain. :)
 
A

Airy R. Bean

Jan 1, 1970
0
You have missed the crucial point and that is
the derivation of the discussion from an
original posting upon the expansion of
cos(wt).

It is inconceivable that anyone with the
qualifications hinted at below could make
such a blunder in that given context.
 
A

Airy R. Bean

Jan 1, 1970
0
Sorry, OM, but you are not right.

Even with 't' and'w' limited to the domain
of real numbers, 'j' is complex.

If you had also intimated that 'j' was limited to
the said domain, then your statement below
would be correct, but would then lack any credence
in a NG devote to electrical engineering.

Clearly, the quantity 'e^(-jwt)' does in fact decrease as 't' moves in the
positive direction (i.e. increases) if 'w' is constant and 't' and 'w' are
limited to the domain of real numbers (not imaginary).
 
C

Chimera

Jan 1, 1970
0
Airy R. Bean said:
If the sentiment expressed in the thread title were to
be expressed by someone with two degrees, one in
electronics and the other in mathematics, someone who
holds a position of authority in the training of electrical
engineering newcomers, what would such a statement say
about the state of engineering education today? (Especially
when that statement had been made in response to the
identity, "cos(wt) = 1/2 * ( e^(jwt) + e^(-jwt) )2 such that
the context was clear?)

I suggest you go and attend one of their training courses as they clearly
have a far better insight into maths than you.


Chimera
 
C

Chimera

Jan 1, 1970
0
Airy R. Bean said:
You have missed the crucial point and that is
the derivation of the discussion from an
original posting upon the expansion of
cos(wt).

It is inconceivable that anyone with the
qualifications hinted at below could make
such a blunder in that given context.

What qualifications do you have?

Chimera
 
C

Chimera

Jan 1, 1970
0
Airy R. Bean said:
Sorry, OM, but you are not right.

Even with 't' and'w' limited to the domain
of real numbers, 'j' is complex.

If you had also intimated that 'j' was limited to
the said domain, then your statement below
would be correct, but would then lack any credence
in a NG devote to electrical engineering.

Try again.

Chimera
 
C

Chimera

Jan 1, 1970
0
tony said:
I guess I'm having a case of the terminal stupids: I seem to remember (and
Perry's Engineering Manual, 2nd Edition, (c) 1967 confirms this)

that

e ^(-yi) = cos(y) - (i) sin(y).

so its value hardly decreases for increasing real y

Now anyone can change conventions and redefine terms, but within the profession
this newsgroup represents one had better constrain himself to using
conventional terminology if clear communication is the goal.

In many years of working in DSP I must have seen this 100s of times. Read
the earlier threads see if you can spot Airy's error, it is almost as
obvious as it is common. I'd look at the rotating vector model very
carefully, if I were you.

Chimera
 
F

Frank Turner-Smith G3VKI

Jan 1, 1970
0
Airy R. Bean said:
Sorry, OM, but you are not right.

Even with 't' and'w' limited to the domain
of real numbers, 'j' is complex.
'j' is hardly complex, it's just an imaginary constant with a value of
SQRT(-1)
 
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