how to use vpasolve to solve the equation sin(x)==0 in the range of (0,5] instead of [0,5]?
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I want to solve sin(x)=0 in the open interval of (0,5], but it seems vpasolve supports close interval only. So it is not able to give the answer I want.
Of course we can use solve and assume instead, but in my real case I have to use vpasolve because of accuracy reason.
2 Comments
Dyuman Joshi
on 23 Sep 2023
"Of course we can use solve and assume instead, but in my real case I have to use vpasolve because of accuracy reason."
Can you elaborate on this?
Are you saying that there accuracy issues when using symbolic variables with solve?
Answers (1)
Walter Roberson
on 23 Sep 2023
vpasolve() does not support open or semi-open intervals.
The trick is to use
syms x
sol = vpasolve(sin(x)==0, x, [1e-63 5])
I do not understand at the moment why left bounds smaller than 1e-63 appear to be treated as 0, even if you state them symbolically such as sym(10)^-80
9 Comments
David Goodmanson
on 23 Sep 2023
Edited: David Goodmanson
on 24 Sep 2023
syms x
sol = vpasolve(sin(x)/x==0, x, [0 5])
sol =
3.1415926535897932384626433832795
Ok, admittedly it's a method particular to this problem. On the other hand it doesn't hurt to keep in mind that zeros can be removable, just as poles can be removable.
Walter Roberson
on 23 Sep 2023
That suggests,
syms x
sol = pi * vpasolve(sinc(x) == 0, x, [0 5/pi])
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