Difference between revisions of "NSolve Command"

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(* NSolve won't work for functions that are asymptotic to the x-axis. They can often be reformulated though)
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:Finds numerically the list of solutions to the given equation for the given unknown variable with its starting value.
 
:Finds numerically the list of solutions to the given equation for the given unknown variable with its starting value.
 
:{{examples|1=<div>
 
:{{examples|1=<div>
:*<code><nowiki>NSolve[cos(x) = x, x = 0]</nowiki></code> yields ''{0.74}''
+
:*<code><nowiki>NSolve[cos(x) = x, x = 0]</nowiki></code> yields ''{x = 0.74}''
:*<code><nowiki>NSolve[a^4 + 34a^3 = 34, a = 3]</nowiki></code> yields the list ''{-34, 0.99}''.</div>}}
+
:*<code><nowiki>NSolve[a^4 + 34a^3 = 34, a = 3]</nowiki></code> yields ''{a = 0.99}''.</div>}}
  
 
;NSolve[ <List of Equations>, <List of Variables> ]
 
;NSolve[ <List of Equations>, <List of Variables> ]

Revision as of 11:33, 30 July 2015



NSolve[ <Equation> ]
Attempts (numerically) to find a solution for the equation for the main variable. For non-polynomials you should always specify a starting value (see below).
Example:
NSolve[x^6 - 2x + 1 = 0] yields {x = 0.51, x = 1}.


NSolve[ <Equation>, <Variable> ]
Attempts (numerically) to find a solution of the equation for the given unknown variable. For non-polynomials you should always specify a starting value (see below).
Example:
NSolve[a^4 + 34a^3 = 34, a] yields {a = -34.00086498588374, a = 0.9904738885574178}.


NSolve[ <Equation>, <Variable = starting value> ]
Finds numerically the list of solutions to the given equation for the given unknown variable with its starting value.
Examples:
  • NSolve[cos(x) = x, x = 0] yields {x = 0.74}
  • NSolve[a^4 + 34a^3 = 34, a = 3] yields {a = 0.99}.


NSolve[ <List of Equations>, <List of Variables> ]
Attempts (numerically) to find a solution of the set of equations for the given set of unknown variables.
Example:
NSolve[{pi / x = cos(x - 2y), 2 y - pi = sin(x)}, {x = 3, y = 1.5}] yields {x = 3.141592651686591, y = 1.570796327746508}.
Note:
  • If you don't give a starting point like a=3 or {x = 3, y = 1.5} the numerical algorithm may find it hard to find a solution (and giving a starting point doesn't guarantee that a solution will be found)
  • The number of decimals depends on the choosen in global rounding.
  • NSolve won't work for functions that are asymptotic to the x-axis. They can often be reformulated though
  • See also Solve Command and NSolutions Command.
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