How to get == to help solving equations

Hello.

I cant get my matlab to stop putting out logical when i use the == command before trying to solve.

syms y
x = 5*y == 20
solve(x,y)

I can see that it makes sense that matlab says that 5*y is not equal to 20

but my study buddies can use the solve command after on x for the variable y to solve equations in matlab.

Answer 1

[madhan ravi]

You should have the Symbolic Math Toolbox and the license for it to perform the above operation. In order to replicate your message , experimented with the below code:

>> y = 1

y =

     1

>> syms y
x = 5*y == 20
solve(x,y)

 
x =
 
5*y == 20
 
 
ans =
 
4
 
>> 

So probably it has to do with you not having the toolbox/license.

[Henrik Kristiansen]

i just installed the toolbox and it still doesnt output 4 for y

still gives me "logical = 0"

and when i install the toolbox, then the simplify command wont work on some of my other equations in my scripts :s

[madhan ravi]

 which syms -all % what does it show?

[Henrik Kristiansen]

ive fixed it by uninstalling all toolbox's and reinstalling them again.

Thanks for the help tho :)

Answer 2

[Steven Lord]

My guess would be that you had redefined y between the syms call and when you tried to use it as a symbolic variable.

syms y
f = 5*y == 20 % symbolic equation

syms z
z = 2; % z is no longer symbolic
g = 5*z == 20 % logical false as 10 is not equal to 20