On the n-th derivative of the inverse function












8














Given a function $f(x)$, its inverse $g(x)$ is defined as $g(f(x)) equiv x$.



In light of this, the n-th derivative of $g(x)$ can be recursively calculated as follows:



list = {};

For[n = 1, n <= 6, n++,

eqn = D[g[f[x]], {x, n}] == D[x, {x, n}];
var = Derivative[n][g][f[x]];

If[n == 1,
list = Join[list, Solve[eqn, var][[1]]],
list = Join[list, (Solve[eqn, var] /. list)[[1]]]
]

]

list // Expand // TableForm


enter image description here



In MMA you can get this very simply by writing something like this:



Derivative[n][InverseFunction[f]][f[x]]


The question that arises is the following: is the latter formulation using a recursive process like the one shown above or is there a non-recursive formulation?










share|improve this question
























  • Something like Derivative[3][InverseFunction[f]][f[x]]?
    – Szabolcs
    2 days ago










  • @Szabolcs: I was just modifying writing this. Now I have again asked the question, thank you!
    – TeM
    2 days ago










  • Sounds like a math question, not Mathematica ... (it's interesting though)
    – Szabolcs
    yesterday










  • @Szabolcs: In fact you are right. Sometimes, however, some topics are borderline, it is difficult to understand how and where to formulate them, at least for me.
    – TeM
    yesterday
















8














Given a function $f(x)$, its inverse $g(x)$ is defined as $g(f(x)) equiv x$.



In light of this, the n-th derivative of $g(x)$ can be recursively calculated as follows:



list = {};

For[n = 1, n <= 6, n++,

eqn = D[g[f[x]], {x, n}] == D[x, {x, n}];
var = Derivative[n][g][f[x]];

If[n == 1,
list = Join[list, Solve[eqn, var][[1]]],
list = Join[list, (Solve[eqn, var] /. list)[[1]]]
]

]

list // Expand // TableForm


enter image description here



In MMA you can get this very simply by writing something like this:



Derivative[n][InverseFunction[f]][f[x]]


The question that arises is the following: is the latter formulation using a recursive process like the one shown above or is there a non-recursive formulation?










share|improve this question
























  • Something like Derivative[3][InverseFunction[f]][f[x]]?
    – Szabolcs
    2 days ago










  • @Szabolcs: I was just modifying writing this. Now I have again asked the question, thank you!
    – TeM
    2 days ago










  • Sounds like a math question, not Mathematica ... (it's interesting though)
    – Szabolcs
    yesterday










  • @Szabolcs: In fact you are right. Sometimes, however, some topics are borderline, it is difficult to understand how and where to formulate them, at least for me.
    – TeM
    yesterday














8












8








8







Given a function $f(x)$, its inverse $g(x)$ is defined as $g(f(x)) equiv x$.



In light of this, the n-th derivative of $g(x)$ can be recursively calculated as follows:



list = {};

For[n = 1, n <= 6, n++,

eqn = D[g[f[x]], {x, n}] == D[x, {x, n}];
var = Derivative[n][g][f[x]];

If[n == 1,
list = Join[list, Solve[eqn, var][[1]]],
list = Join[list, (Solve[eqn, var] /. list)[[1]]]
]

]

list // Expand // TableForm


enter image description here



In MMA you can get this very simply by writing something like this:



Derivative[n][InverseFunction[f]][f[x]]


The question that arises is the following: is the latter formulation using a recursive process like the one shown above or is there a non-recursive formulation?










share|improve this question















Given a function $f(x)$, its inverse $g(x)$ is defined as $g(f(x)) equiv x$.



In light of this, the n-th derivative of $g(x)$ can be recursively calculated as follows:



list = {};

For[n = 1, n <= 6, n++,

eqn = D[g[f[x]], {x, n}] == D[x, {x, n}];
var = Derivative[n][g][f[x]];

If[n == 1,
list = Join[list, Solve[eqn, var][[1]]],
list = Join[list, (Solve[eqn, var] /. list)[[1]]]
]

]

list // Expand // TableForm


enter image description here



In MMA you can get this very simply by writing something like this:



Derivative[n][InverseFunction[f]][f[x]]


The question that arises is the following: is the latter formulation using a recursive process like the one shown above or is there a non-recursive formulation?







calculus-and-analysis






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited yesterday

























asked 2 days ago









TeM

1,886620




1,886620












  • Something like Derivative[3][InverseFunction[f]][f[x]]?
    – Szabolcs
    2 days ago










  • @Szabolcs: I was just modifying writing this. Now I have again asked the question, thank you!
    – TeM
    2 days ago










  • Sounds like a math question, not Mathematica ... (it's interesting though)
    – Szabolcs
    yesterday










  • @Szabolcs: In fact you are right. Sometimes, however, some topics are borderline, it is difficult to understand how and where to formulate them, at least for me.
    – TeM
    yesterday


















  • Something like Derivative[3][InverseFunction[f]][f[x]]?
    – Szabolcs
    2 days ago










  • @Szabolcs: I was just modifying writing this. Now I have again asked the question, thank you!
    – TeM
    2 days ago










  • Sounds like a math question, not Mathematica ... (it's interesting though)
    – Szabolcs
    yesterday










  • @Szabolcs: In fact you are right. Sometimes, however, some topics are borderline, it is difficult to understand how and where to formulate them, at least for me.
    – TeM
    yesterday
















Something like Derivative[3][InverseFunction[f]][f[x]]?
– Szabolcs
2 days ago




Something like Derivative[3][InverseFunction[f]][f[x]]?
– Szabolcs
2 days ago












@Szabolcs: I was just modifying writing this. Now I have again asked the question, thank you!
– TeM
2 days ago




@Szabolcs: I was just modifying writing this. Now I have again asked the question, thank you!
– TeM
2 days ago












Sounds like a math question, not Mathematica ... (it's interesting though)
– Szabolcs
yesterday




Sounds like a math question, not Mathematica ... (it's interesting though)
– Szabolcs
yesterday












@Szabolcs: In fact you are right. Sometimes, however, some topics are borderline, it is difficult to understand how and where to formulate them, at least for me.
– TeM
yesterday




@Szabolcs: In fact you are right. Sometimes, however, some topics are borderline, it is difficult to understand how and where to formulate them, at least for me.
– TeM
yesterday










1 Answer
1






active

oldest

votes


















8














D[InverseFunction[f][x], {x, 6}]


Towards the question whether this is computed recursively: I guess so from analyzing the Trace produced by executing the code:



Table[
Length@Trace[
D[InverseFunction[f][x], {x, k}]
],
{k, 1, 12}]



{6, 7, 7, 10, 13, 18, 25, 36, 51, 73, 103, 145}







share|improve this answer























  • Ok, get it, thank you!
    – TeM
    2 days ago











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1 Answer
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active

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1 Answer
1






active

oldest

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active

oldest

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active

oldest

votes









8














D[InverseFunction[f][x], {x, 6}]


Towards the question whether this is computed recursively: I guess so from analyzing the Trace produced by executing the code:



Table[
Length@Trace[
D[InverseFunction[f][x], {x, k}]
],
{k, 1, 12}]



{6, 7, 7, 10, 13, 18, 25, 36, 51, 73, 103, 145}







share|improve this answer























  • Ok, get it, thank you!
    – TeM
    2 days ago
















8














D[InverseFunction[f][x], {x, 6}]


Towards the question whether this is computed recursively: I guess so from analyzing the Trace produced by executing the code:



Table[
Length@Trace[
D[InverseFunction[f][x], {x, k}]
],
{k, 1, 12}]



{6, 7, 7, 10, 13, 18, 25, 36, 51, 73, 103, 145}







share|improve this answer























  • Ok, get it, thank you!
    – TeM
    2 days ago














8












8








8






D[InverseFunction[f][x], {x, 6}]


Towards the question whether this is computed recursively: I guess so from analyzing the Trace produced by executing the code:



Table[
Length@Trace[
D[InverseFunction[f][x], {x, k}]
],
{k, 1, 12}]



{6, 7, 7, 10, 13, 18, 25, 36, 51, 73, 103, 145}







share|improve this answer














D[InverseFunction[f][x], {x, 6}]


Towards the question whether this is computed recursively: I guess so from analyzing the Trace produced by executing the code:



Table[
Length@Trace[
D[InverseFunction[f][x], {x, k}]
],
{k, 1, 12}]



{6, 7, 7, 10, 13, 18, 25, 36, 51, 73, 103, 145}








share|improve this answer














share|improve this answer



share|improve this answer








edited 2 days ago

























answered 2 days ago









Henrik Schumacher

48.6k467137




48.6k467137












  • Ok, get it, thank you!
    – TeM
    2 days ago


















  • Ok, get it, thank you!
    – TeM
    2 days ago
















Ok, get it, thank you!
– TeM
2 days ago




Ok, get it, thank you!
– TeM
2 days ago


















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