Is there a function I can use to find out when a statement is true?

Hello,

I'm new to matlab.

Is there a function I can use to find out when a statement is true?

Simple example: for which "x" the equation is true.

1+x = 3

Can somebody help me?

Alex

Answer 1

[Sulaymon Eshkabilov]

in your case, if ... else ... end structure should work very well.

Answer 2

[Ameer Hamza]

See this. It uses symbolic toolbox to solve the equations.

syms x
eq = 1+x == 3;
sol = solve(eq);

Result:

>> sol
sol =
2

See documentation of solve() function for more examples.

[Adam Roudi]

Great. Thanks.

I tested a few functions with your tips and they worked well.

However, this one doesn't work:

1/(10^x(10^x+1)).

any ideas?

[Karan Mehta]

Hi Alexander

Can you please share the error message when you solve this equation. Also, in order to solve 1/(10^x * (10^x+1)), represent this in form of an equation ,eg. 1/(10^x*(10^x+1)) == "some value". Then it would work. Like i tried the following

>> syms z

>> eq = 1/(10^z * (10^z + 1)) == 10

eq =

1/(10^z*(10^z + 1)) == 10

>> sol = solve(eq)

sol =

log(- 35^(1/2)/10 - 1/2)/log(10)

log(35^(1/2)/10 - 1/2)/log(10)

[Ameer Hamza]

I got the same answer as Karan. But if you are using release older than R2020a, than it is possible that MATLAB didn't return a solution. It seems that MATLAB has made some improvements to the symbolic engine in the new release, and it is able to solve equations that were not possible before. In that case, you will need to rely on a numerical solution

eq = @(x) 1/(10^x*(10^x+1)) - 10;
sol = fsolve(eq, rand);

The downside is that it can only give one solution at a time.