'solve' Command - Only shows one value

Hi,

In another pc where I test this line:

double(solve('1=2.*sin(m)'))

Return values are 0.5236 and 2.6180. However, in my computer only returns the 0.5236 value. How I show the second value?

Thank you.

[Oleg Komarov]

I get an error:

Error using solve>processString (line 337)
' 1=2.*sin(m) ' is not a valid expression or equation.

What is your MATLAB version?

[Cristian]

My error. Excuse me.

double(solve('1=2*sin(m)'))

Without the dot.

[bym]

the documentation says the string can not contain an equals sign. Here are my results (R2008b)

solve('1-2*sin(x)')

ans =

       pi/6
   (5*pi)/6

[Walter Roberson]

The equals sign can appear in modern MATLAB.

Answer 1

[Walter Roberson]

MATLAB 7.0 used Maple for its Symbolic Mathematics Toolbox. Maple only bothers to find a single value in this situation. When Maple is asked to find AllSolutions, it says they are

(1/6)*Pi + (2/3)*Pi*_B1 + 2*Pi*_Z1

The way to read this is that _B1 can be 0 or 1, and _Z1 is any integer (positive or negative). So solutions are at

[...], -11*Pi/6, -7*Pi/6, Pi/6, 5*Pi/6, 13*Pi/6, 17*Pi/6, [...]

Answer 2

[bym]

try this (without using string input)

syms t
  >> double(solve(1-2.*sin(t)))

ans =

      0.5236
      2.6180

[Cristian]

Hi.

This line produces me the same output as the first code.

>> syms t;
>> double(solve(1-2.*sin(t)))

ans =

      0.5236

Another question. What is the function of syms t?

Thanks.

[bym]

syms t % constructs a symbolic object

what does

solve(1-2*sin(t))

return?

[Cristian]

This:

>> solve('1-2*sin(t)')

ans =

1/6*pi

[Walter Roberson]

Which MATLAB version are you using?

[Cristian]

Version 7.0