How to check an inequality of a variable is true or not in MatLab? isAlways -- MatLab

How to check an inequality of a variable is true or not in MatLab? 

e.g. 

check abs(x)>=0 where x is any number.

or 

check (2*x+1>=0) where x>=0;

[Ans]

isAlways command

[Description]

isAlways(<expre>) 

it will return true if the expression <expre> is Alaways true.

it will return false if the expression <expre> is Alaways false.

If the expression <expre> is Unknown (i.e. it is not certain ) (i.e.it maybe true or false), it will throw warning (by default ,without other argument) and return false.

you can change the default behavoiur by setting its <Name>

[Syntax]

isAlways(<expre>);

isAlways(<expre>,<Name>,<Value>);

Set <Name> as <Value>.

e.g. is on at buttom.

more details on:

Check whether equation or inequality holds for all values of its variables - MATLAB isAlways (mathworks.com)

e.g.

clear

clc

%true

syms x;

assume(x<0);

isAlways(x<0)

fprintf("1\n");

%Unknown

syms y

isAlways(y)

fprintf("2\n");

%Unknown to false

syms z

isAlways(y,'Unknown','false')

fprintf("3\n");

%true

syms a

isAlways(abs(a)>=0,'Unknown','false')

fprintf("4\n");

%true

syms b

isAlways((sin(b)*sin(b)+cos(b)*cos(b))==1,'Unknown','false')

fprintf("5\n");

%false

syms c

isAlways(c>1,'Unknown','true')

fprintf("6\n");

%false

syms d

isAlways(abs(d)<-1,'Unknown','true')

fprintf("7\n");

%{

all output:

ans =

logical

1

1

Warning: Unable to prove 'y'.

> In symengine

In sym/isAlways (line 41)

In assume_example (line 11)

ans =

logical

0

2

ans =

logical

0

3

ans =

logical

1

4

ans =

logical

1

5

ans =

logical

1

6

ans =

logical

0

s7

%}