, . , , collect; expand; factor; simplify simple ( , MATLAB , , simplify, , , ), ; subs subexr.
.
.
:
>> syms a x
>> f=a*log(x)-x*log(x)-x-a;
>> collect(f,log(x))
ans =
(a - x)*log(x) - a - x
.
:
>> syms x y a
>> f=x*y+a*x*y+y*x^2-a*y*x^2+x*y^2+a*x
f =
a*x + x*y + x*y^2 + x^2*y - a*x^2*y + a*x*y
>> collect(f,'x')
ans =
(y - a*y)*x^2 + (a + y + a*y + y^2)*x
>> collect(f,'y')
ans =
x*y^2 + (x + a*x - a*x^2 + x^2)*y + a*x
, collect,
collect(expr [, var])
expr var ( ), , x.
. :
>> syms alpha beta
>> expand(cos(alpha+beta))
ans =
cos(alpha)*cos(beta) - sin(alpha)*sin(beta)
. :
>> syms x y
>> expand(exp(x+y))
ans =
exp(x)*exp(y)
. :
>> syms x
>> f=(x+1)*(x+2)*(x+3)
f =
(x + 1)*(x + 2)*(x + 3)
>> expand(f)
ans =
x^3 + 6*x^2 + 11*x + 6
. :
>> syms x
>> f=x^3+8
f =
x^3 + 8
>> factor(f)
ans =
(x + 2)*(x^2 - 2*x + 4)
, factor , .
.
:
>> syms x
>> f=(4-x^2)/(x+2)
f =
-(x^2 - 4)/(x + 2)
>> simplify(f)
ans =
2 - x
.
:
>> syms x
>> f=sin(x)^2+cos(x)^2
f =
cos(x)^2 + sin(x)^2
>> simplify(f)
ans =
, subs(expr [, var1, var2]) , subs(expr) expr , . subs(expr [, var1]) expr var1; subs(expr [, var1, var2]) expr var1 var2. , :
|
|
>> x=1;
>> subs(x^2-2*x+1)
ans =
>> syms a b
>> p=sym('5*x^4-7*x^2+4')
p =
5*x^4 - 7*x^2 + 4
>> p=subs(p,a-b)
p =
5*(a - b)^4 - 7*(a - b)^2 + 4
>> subs(p,[a,b],[2,1])
ans =