MATLAB Answers

## fzero help

Asked by buxZED

### buxZED (view profile)

on 24 Feb 2011
Accepted Answer by Honglei Chen

### Honglei Chen (view profile)

```y=@(T) I*T*sind(A)-(0.5*G*(T^2));
root = fzero(y, 0)
```

abouve eqation is for a projectile that projected at an angle (gose in a kind of ar half oval shape)

want to find the time it hist ground but fzero only gives me the biginning which is 0

buxZED

### buxZED (view profile)

on 24 Feb 2011

it worked Matt
thank you so much
and also ~ would allow me to use matlab in many new ways
thank you again :D

Matt Tearle

### Matt Tearle (view profile)

on 25 Feb 2011

Can I suggest using an initial guess of 2*I*sind(A)/G? Just sayin'...

Matt Fig

### Matt Fig (view profile)

on 25 Feb 2011

Come on now, Matt! Where is the fun of solving the equation with your brain instead of making MATLAB do it?

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## 1 Answer

### Honglei Chen (view profile)

Answer by Honglei Chen

### Honglei Chen (view profile)

on 17 Sep 2012
Accepted answer

The anwser is in the comments above

From Matt Fig

```rt = 0;
d = .1;
cnt = 1;
while rt<.1
rt = fzero(y,rt+d*cnt);
cnt = cnt + 1;
end
```

Matt Fig

### Matt Fig (view profile)

on 17 Sep 2012

Digging deep, Honglei! How did you come across this one from over a year ago?

Honglei Chen

### Honglei Chen (view profile)

on 17 Sep 2012

I'm helping cleaning up some old, unanswered questions :)

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