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2-Guest

## help to find mistake

Hi,

I am new with mathcad, Could somebody help solve problem. Why temperature value is marked red color?

1 ACCEPTED SOLUTION

Accepted Solutions
24-Ruby V
(To:SZ_11156868)

@SZ_11156868 wrote:

Why is it so difficult? Why is it not working like that? I make a range and put it into the function.

Actually it IS working like that!!

You make a range (n), create a vector (T) by using the range to index the elements of that vector and then use the elements of this vector as arguments of your function rho.

You may even put the whole vector T as one argument in your function (without using the range n) and while it would not be necessary in case of your function it would be good habit to vectorize the function call:

If you would like us to find the error in your sheet and to tell you, why it does not work for you, you would have to post your worksheet, not just pictures. And it would be a good idea to say which version of Prime you are using.

BTW, my best guess is that you are not using the matrix index when you try to create your vector T but are using the literal index (subscript). This can't work.

See the pictures here: Solved: Re: how to do element product in two column vector...

BTW, your initial question was why °C^-1 threw an error. The reason is that most units are just factors, a quantity is multiplied with. This is true for °DeltaC, which basically is just K (Kelvin). So for a simple costant factor writing ...^-1 is OK, its just the reciprocal value. But the unit °C is different. Converting from the default unit Kelvin to degree Celsius is not just a multipication with a constant factor (like the conversion of meter to feet) but also involves a scale shift. Therefore °C is implemented as a function (it can't be seen as it looks like any other unit). But being a function the operator ...-1 does not make sense and so is not accepted. You may divide by 1 °C instead if you really would need to do so.

6 REPLIES 6
21-Topaz I
(To:SZ_11156868)

Because alpha is a function of change in temperature not a property of a fixed temperature.

Cheers

Terry

21-Topaz I
(To:terryhendicott)

Why is it so difficult? Why is it not working like that? I make a range and put it into the function.

20-Turquoise
(To:SZ_11156868)

Not T sub n, but T [ n, vector index n.

24-Ruby V
(To:SZ_11156868)

@SZ_11156868 wrote:

Why is it so difficult? Why is it not working like that? I make a range and put it into the function.

Actually it IS working like that!!

You make a range (n), create a vector (T) by using the range to index the elements of that vector and then use the elements of this vector as arguments of your function rho.

You may even put the whole vector T as one argument in your function (without using the range n) and while it would not be necessary in case of your function it would be good habit to vectorize the function call:

If you would like us to find the error in your sheet and to tell you, why it does not work for you, you would have to post your worksheet, not just pictures. And it would be a good idea to say which version of Prime you are using.

BTW, my best guess is that you are not using the matrix index when you try to create your vector T but are using the literal index (subscript). This can't work.

See the pictures here: Solved: Re: how to do element product in two column vector...

BTW, your initial question was why °C^-1 threw an error. The reason is that most units are just factors, a quantity is multiplied with. This is true for °DeltaC, which basically is just K (Kelvin). So for a simple costant factor writing ...^-1 is OK, its just the reciprocal value. But the unit °C is different. Converting from the default unit Kelvin to degree Celsius is not just a multipication with a constant factor (like the conversion of meter to feet) but also involves a scale shift. Therefore °C is implemented as a function (it can't be seen as it looks like any other unit). But being a function the operator ...-1 does not make sense and so is not accepted. You may divide by 1 °C instead if you really would need to do so.

2-Guest
(To:Werner_E)