Asked by Gavin Seddon
on 13 Feb 2019 at 11:33

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.

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

Accepted Answer

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

Walter Roberson
on 14 Feb 2019 at 22:58

Gavin Seddon
on 15 Feb 2019 at 11:42

Hello, DOUBLE gave unusual answers

whilst simplify to give 2 numbers did not work.

How would I accomplish this?

GS.

Walter Roberson
on 15 Feb 2019 at 13:06

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## 2 Comments

## Gavin Seddon (view profile)

Direct link to this comment:https://www.mathworks.com/matlabcentral/answers/444731-calculating-x-when-y-is-0#comment_671201

## madhan ravi (view profile)

Direct link to this comment:https://www.mathworks.com/matlabcentral/answers/444731-calculating-x-when-y-is-0#comment_671202

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