fzero
--------fzero('',x)----------
fzero('',x) x, , , x. ( )
NaN
(Not-a-Number )
x1=fzero('x-5',4)
x2=fzero('x-5',2)
x3=fzero('2^x-8',0)
x4=fzero('2^x-7',0)
x5=fzero('0.25*x+sin(x)-1',5)
>> x1=fzero('x-5',4)
x1 =
>> x2=fzero('x-5',2)
x2 =
>> x5=fzero('0.25*x+sin(x)-1',5)
x5 =
5.8128
:
.
1
y=x.^3-9*x.^2+26.*x-24;
x=1.5:0.5:4.5;
y=x.^3-9*x.^2+26.*x-24;
,
, .
plot(x,y),grid %
, y=x.^3-9*x.^2+26.*x-24; .
x1=fzero('x^3-9*x^2+26*x-24',1.8)
x2=fzero('x^3-9*x^2+26*x-24',3.1)
x3=fzero('x^3-9*x^2+26*x-24',4.3)
% 2, 3, 4.
>> x=1.5:0.1:4.5;
>>
>> y=x.^3-9*x.^2+26.*x-24;
>> plot(x,y),grid
1.8 3.1 4.3
>> x1=fzero('x^3-9*x^2+26*x-24',1.8)
x2=fzero('x^3-9*x^2+26*x-24',3.1)
x3=fzero('x^3-9*x^2+26*x-24',4.3)
x1 =
x2 =
3.0000
x3 =
--------------------------------------------
2
Y=x.^2-5*x+6
x=-2:0.2:5;
plot(x,x.^2-5*x+6)
Grid on;
x=fzero('x^2-5*x+6',1)
x=fzero('x^2-5*x+6',4)
% 2, 3.
x=fzero('x^2-5*x+6',1)
x=fzero('x^2-5*x+6',4)
x =
x =
3.0000
2) :
%-------------fzero('',[x1,x2])------------
1
x1_1=fzero('x^3-9*x^2+26*x-24',[1.8 4.5])% .. fzero('',[x1,x2]) .
x1_1=fzero('x^3-9*x^2+26*x-24',[1.8 2.3]) (x1_1 = 2.0000)
--------------------------------------------------------------------------------
3
Y=cos(x);
x=-2*pi:0.1:2*pi;
Plot(x,cos(x))
x=fzero('cos',[1 3])
x=fzero('cos(x)',[1 3])
= fzero(@cos.[1 3])
'cos',[-5 5], .. - .
[1 3]
= 1.57
4
0.25*x+sin(x)-1;
|
|
x=0:0.1:10;
plot(x,0.25*x+sin(x)-1)
grid on; % , %[0.5 1], [2 3], [5 6]
x1=fzero('0.25*x+sin(x)-1',[0.5 1])
x2=fzero('0.25*x+sin(x)-1',[2 3])
x3=fzero('0.25*x+sin(x)-1',[5 6])
x1 =
0.8905
x2 =
2.8500
x3 =
5.8128
3) :
-------------- fzero('',x,eps) --------
4
x4=fzero('0.25*x+sin(x)-1',5,0.00001)
x4=fzero('0.25*x+sin(x)-1',[5 6],0.00001)
-------------------------------------------------------------
4) \
y=0.25*x+sin(x)-1 - fun5.m fun5.m , .
, sin(x) (), , f(x), M--. , fe=@exp; M-.
function f=fun5(x); ; fun5
f=0.25*x+sin(x)-1;
x1=fzero('fun5',[0.5 1])
>> x1=fzero('fun5',[0.5 1])
x1 =
0.8905
@
x2=fzero(@fun5,[2 3])
>> x2=fzero(@fun5,[2 3])
x2 =
2.8500
x3=fzero('fun5',6)
>> x3=fzero('fun5',6)
x3 =
5.8128
roots
1
() y=x2-5x+6
y=[1 -5 6]; % x2-5x+6=0
x=roots(y);
Vpa(x,2)
ans =
3.0
2.0
2
x3-9*x2+26*x-24=0
y=[1 -9 26 -24]; %
x=roots(y);
Vpa(x,2)
%: 4 3 2
3
24 - 83 + 82 - 1
disp(' 2^4 - 8^3 + 8^2 - 1')% .
% :
p=[2 -8 8 0 -1];
Roots(p)
% 2.3066; 1.5412; 0.4588; -0.3066
:
p=[2 -8 8 0 -1];p -,
x=-1:0.1:3; , X
y=polyval(p,x); ,
plot(x,y,'-k'),grid
roots(p)% 2.3066; 1.5412; 0.4588; -0.3066
___________________________________________________
solve