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calculating x when y is > 0

Asked by Gavin Seddon on 13 Feb 2019 at 11:33
Latest activity Commented on by Walter Roberson
on 15 Feb 2019 at 13:06
Hello
I have plotted a changing distance (d(x)) with time using cftool and calculated the function. Its derivative was calculated and this is v(x). when plotted with fplot the initial Y values are 0. I am calculating the x position at which this rises above the x axes (y>0). To do this i made v(x) equivalent to 1 (==1) and evluated x yet:
>>v(x)==1
ans =
(4119*x^2)/10000 - (1787*x)/5000 + 891/2500 ==1
>> eval x
x =
x
Will someone please help to calculate this? i can measure the x value directly. It is preferable to standardise this procedure.
GS.

  2 Comments

Hello, I tried
solve (x)
ans =
0
does this help?
GS.
madhan ravi
on 14 Feb 2019 at 10:06
Are you asking or stating?

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1 Answer

Answer by Walter Roberson
on 14 Feb 2019 at 11:34
 Accepted Answer

solve(v(x)==1,x)

  6 Comments

I am not sure what you mean by "solve each quadratic equation" ? Perhaps you want to double() the result of solve() to get the floating point equivalent ?
Hello, DOUBLE gave unusual answers
whilst simplify to give 2 numbers did not work.
How would I accomplish this?
GS.
Give an example of the kind of output you want to see, taking into account that the exact solution will involve sqrt()

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