i am trying to find an x value when my y value is equal to 0

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Patrick Deed
Patrick Deed 2020-9-1
评论： Rik 2020-9-2
i am trying to find an x value when my y value is equal to 0
here is what i have so far (this is not giving me the x value but instead displaying
ans =
1×0 empty double row vector
theta=45
h=1.5
g=9.8
v=4
t=0:0.001:1
x=v*cos(theta*3.14/180)*t
y=h+v*sin(theta*3.14/180)*t-0.5*g*t.^2
plot(x,y)
a=find(y<0)
find(y==0,1)

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回答（1 个）

Rik
Rik 2020-9-1
The chance that you end up with a value that is exactly 0 is quite small. You can use code like below as an alternative.
[~,idx]=min(abs(y));
smallest_y=y(idx);
  2 个评论
Patrick Deed
Patrick Deed 2020-9-1
thanks a lot Rik,
but it is a task to use the find function to locate this value and another code will not be accepted
Rik
Rik 2020-9-2
Then you must use a tolerance, or adjust your x values so that you actually have a 0. Using a tolerance in this context uses a similar idea to the code above. What do you think you should be using?
Also, you should mention it if you post a homework question.

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