Math (geometry) problem. $20 for best solution!

[Beja]

Hi,
Here is a math problem that I need to solve.. Please see the attachment.
I have $25 (about 15 pounds sterling) for best answer with b4a demo.
In the attached image, I need to know how to calculate the
lengths of the RED distances (lines) as the pointer moves around Axis X
Please put your solution function in b4a example.

 

[sorex]

are you sure you only need the red lenght?

not the blue or blue+red ?

 

[KitCarlson]

Are the blue lines radi of a circle? If so the math is trivial, it not it the solution is more complex.

 

[LucaMs]

I have not yet read the problem and I have already solved it.

The problem is that you offer $ 20 in the title but then you say you have $ 25, so someone cheats

(now i can read the rest)

 

[LucaMs]

X must be between 0 and (center or diameter).

Each time, the length is the hypotenuse of a right triangle

then:

Sqrt (Power(X,2), Power(Y,2))

P.S. Y is the point on a side of the square!

I know, the answer is not complete, but since I do not want the prize, I indicate only the track, not the complete code


forget it. I read it wrong. x is fixed? In addition, you want the red lines.

then it becomes a more interesting challenge, with sines and cosines

 

[sorex]

maybe he has $25 but only want to spend $20 of it?

he also didn't tell which variable he has, does he have the box coords or the circle ones?

 

[LucaMs]

maybe he has $25 but only want to spend $20 of it?

he also didn't tell which variable he has, does he have the box coords or the circle ones?

box coords are simple: each side is radius * 2

we don't need the exact values

(ah he wants to save even $ 5 huh)

 

[sorex]

for straight lines yes, that rule won't work with none 0/90 degrees angles tho

 

[klaus]

Is this what you are looking for ?

The routine to calculate the red length:

'dx is the distance of x from the center, positive to the right
Sub CalcLength(dx As Double) As Double
    Dim alpha As Double

    x2 = dx
    alpha = ACos(Abs(dx / Radius))
    y2 = Radius * Sin(alpha)
    If alpha > cPI / 4 Then
        y1 = Radius
        x1 = Radius / Tan(alpha) * dx / Abs(dx)
    Else
        y1 = Radius * Tan(alpha)
        x1 = Radius * dx / Abs(dx)
    End If
    Return Sqrt((x2 -x1) * (x2 -x1) + (y2 -y1) * (y2 -y1))
End Sub

 

[thedesolatesoul]

Length of red lines = r . (Sqrt( sin(angle)^2 + 1) - 1)

 

[LucaMs]

Bravissimo, Klaus ! (come sempre )

very good Klaus (as always)

(IDE warned me that my version is... old )

P.S. Klaus, you would be able to solve this issue, I know.

 

[Beja]

Thanks to all who responded this question..
And Klaus wins the prize!
desolatesoul solution looks compact. I didn't test it though.. but there is no demo container.
@ lukaMs: Thanks to you and sorex for the sarcastic comments, realy cool!
If someone put a statement or promise, on the title, then later he put another
statement or promise, then it is the last statement that's valid. I am sure you know but just a reminder.
but your comment was cool and I give it a big LIKE.

 

[LucaMs]

Thanks to all who responded this question..
And Klaus wins the prize!
desolatesoul solution looks compact. I didn't test it though.. but there is no demo container.
@ lukaMs: Thanks to you and sorex for the sarcastic comments, realy cool!
If someone put a statement or promise, on the title, then later he put another
statement or promise, then it is the last statement that's valid. I am sure you know but just a reminder.
but your comment was cool and I give it a big LIKE.

Sorry, Beja, i like to joke

 

[Beja]

Never mind.. I also like to joke and read jokes.

 

[Beja]

Hi thedesolatesoul,
Trying to implement your code, I got the error msg saying text format not correct
Any information appreciated.. thanks in advance

rad = 100
ang = 45
leng = rad * (Sqrt( Sin(ang)^2 + 1) - 1)
Log leng

Error description: Input string was not in a correct format.
Occurred on line: 36
leng = rad . (Sqrt( Sin(ang)^2 + 1) - 1)

 

[NJDude]

This should be correct:

leng = rad * (Sqrt(Power(Sin(ang),2) + 1) - 1)

 

[thedesolatesoul]

Also if you want to specify ang in degrees then use SinD instead of Sin.
Also I havent tried the code myself!

 

[Beja]

thedesolatesoul, perfect!
Well done and take my word, you don't need to try it!.
After NJDude adjustment now working and I test it with all values for ang.

rad = 100
For ang = 1 To 90
leng = rad * (Sqrt(Power(SinD(ang),2) + 1) - 1)
Log(leng)
Next

Thanks to both of you guys.

 

[JoanRPM]

Sorry Beja, but this code dosen't work.
In your code if "ang" is 45º, then "leng" must be 41.42, not 22.47 as your formula says.

Try this one:

Dim r, x As Double

r = 100
For ang = 0 To 45
    x = Sqrt(Power((r),2)/(1-Power(SinD(ang),2))) - r
    Log(ang & "= " & x)
Next

It's only valit from 0 to 45 degres. You must add code to solve this!

Regards.

 

[Beja]

Hi Joan,
Thanks..
will check this and get back to you.

BTW: did you test it in real device or the emulator?