How to solve for x in an sin equation?

Hi MATLAB wizards

I am currently trying to solve the following equation; -7sin(x/7)=0 using symbolic algebra and the solve function in MATLAB.

The code that I used is as follows:

syms x

solve( (-7*sin(x/7)),x)

This code returns the value 0, which is one of the solutions, the other one is 7*pi.

So how can I produce both of these solutions?

Any form of help would be appreciated.

Answer 1

[John D'Errico]

No. There are INFINITELY many solutions. So you cannot say you want the OTHER solution. You can simply enough find a positive solution though.

syms x positive
solve( (-7*sin(x/7)),x)
ans =
7*pi

[JoBrr]

Yes you are right there are many solutions.

But this seems to do the trick.

Cheers for the help.

Answer 2

[David Hill]

[solx,parameters,conditions] = solve(eqn,x,'ReturnConditions',true);

[JoBrr]

yeah that seems to work @David Hill.

But the output is like this:

solx =

7*pi*k

parameters =

k

conditions =

in(k, 'integer')

Not sure if I understand the k and conditions bits.

Here's the code I used in conjunction with yours:

eqn=-7*sin(x/7);

[solx,parameters,conditions] = solve(eqn,x,'ReturnConditions',true)