Cos coming up with NaN

[dantm]

 BeforeInverse= ((2nd.Text ^2 + 3rd.Text ^ 2 - 1st.Text ^ 2) / (2 * 2nd.Text * 3rd.Text))
                Calculation.Text = Math.Acos(BeforeInverse/ Math.PI * 180) 

The above is using the cosine formula which has been rearranged to solve for the angle.
When i calculate, it comes up with NaN and i'm not dividing by 0. What does NaN mean and is there an error with the above code?

[keystone_paul]

NaN means "Not a Number"

The first thing that leaps out from your code is you are doing mathematical operations on textboxes.

You should convert 2nd.text, 3rd.text into numbers - either singles, doubles or integers depending on what you expect.

[dantm]

So do i do that by going for example Dim 1st as Double = 1st.Text?

[keystone_paul]

Yes, although you can't have a variable name starting with a number.

[dantm]

Okay thanks mate.

Another problem

I went: Dim First as Double = 1st.Text

And it came up saying some error about NullReferenceException was unhandeled. Then it said use New?

[keystone_paul]

I'm confused as to how you can have a textbox named "1st"

This is just a variable like any other, and so should be subject to the same naming rules.

[dantm]

Sorry dude, i dunno why i typed the abbreviations did it quick. I retyped out the code shoulda just copy and pasted. Yeah they are all first and second and third, but there is still a problem with the way that above is working. NullUnhandledException for
Dim First as Double = First.Text

[keystone_paul]

Actually sorry my mind is not working - haven't read your code properly, you need to parse the text value properly :

        Dim First As Double
        If Double.TryParse(First.Text, First) Then
            'OK
        Else
            'can't convert
        End If

And you need to put code in the If...Else to handle what happens if the content of the text box can't be converted.

[dantm]

I just whipped it in and gave it a go, still NaN.

[keystone_paul]

OK, so have you checked that all First, Second and Third contain valid numbers within the range that you are expecting?

For Acos to work, you need to pass in a value between -1 and +1 - so what does BeforeInverse evaluate to?

[SJWhiteley]

To expand on what Paul is saying, I'd create at least 3 intermediate variables, and variables of the correct data type for each text box.

Convert each text box to a number.
Store the calculated numerator in a variable.
Store the calculated denominator in a variable.
Perform the 'BeforeInverse' calculation.
Convert the BeforeInverse variable to another variable (BeforeInverse / Math * Pi).
Put that variable into your Inverse Cosine (which, as already stated, must be between +/-1).

Then, debug by stepping through: you will find your error within seconds.

[JuggaloBrotha]

Check out this thread: http://www.vbforums.com/showthread.php?t=569582