[11.8] Try solve() for symbolic system solutions
Consider this system of equations:
2x - y + z = a
x + y - 3z = b
3x - 2z = c
The solution for x, y and z depends on the values of a, b and c. solve() can usually find solutions to
these kinds of systems. For example,
solve(2x-y+z=a and x+y-3z=b and 3x-2z=c,{x,y,z})
returns
and
and
and
x
=
c
+
2
$
@1
3
y
=
3
$
b
−
c
+
7
$
@1
3
z
=
@1
a
= −(
b
−
c
)
The notation "@1" indicates an arbitrary constant in the solution. For example, let @1 = k, then
and
and
and
x
=
c
+
2
$
k
3
y
=
3
$
b
−
c
+
7
$
k
3
z
=
k
a
= −(
b
−
c
)
If we let k = 5, b = 3 and c = 7, then a = 4, x = 17/3, y = 37/3 and z = 5. These values are solutions to
the original system.
(Credit to Rick Homard)
[11.9] nSolve() may return "Questionable Accuracy" warning even with good solutions
nSolve() is a reasonably robust numeric solver, but some equations give it difficulty, even when there
are no obvious problems such as singularities. Futher, nSolve() may give the "Questionable Accuracy"
warning in the status line, for solutions that seem valid. In these cases, nSolve() will take longer to
return the answer, even when it returns nearby solutions quickly.
These two programs illustrate the problem:
solvebug(vf)
func
local vfs,tapx
©Find estimate tapx for solution
ln(1000*(vf-.015))
→
vfs
polyeval({3.618919682914,
⁻
31.003830334444,76.737472978603,
⁻
68.237201523917,262.4
6139741751,84.916629306139},vfs)+polyeval({
⁻
3.9287348339733
⁻
7,5.9179552041553
⁻
5,
⁻
0.0036896155610467,0.12308990642018,
⁻
2.7560332337098,0},1/vfs)
→
tapx
©Find solution, with bounds from tapx
nsolve(vfts120(t)=vf,t)|t
≥
tapx-.4 and t
≤
min({tapx+.4,705.47})
Endfunc
vfts120(ts)
11 - 8
Summary of Contents for TI-92+
Page 52: ...Component side of PCB GraphLink I O connector detail 1 41...
Page 53: ...LCD connector detail PCB switch side 1 42...
Page 54: ...Key pad sheet contact side Key pad sheet key side 1 43...
Page 55: ...Key cap detail 1 44...
Page 57: ...Component side of PCB with shield removed A detail view of the intergrated circuits 1 46...
Page 410: ...void extensionroutine2 void Credit to Bhuvanesh Bhatt 10 4...
