Math Is Fun Forum

  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#27 Formulas » Lemniscate functions » 2024-02-24 23:54:43

lanxiyu
Replies: 0

Notations:








Specific values:


















Differential equations:


























Pythagoras-like identities:





Opposite angle identities:








Double angle identities:







Triple angle identities:





Half angle identities:






Angle sum and difference identities:







Translation by real quarter-periods:






Translation by imaginary quarter-periods:






Translation by real half-periods:








Translation by imaginary half-periods:








Quarter-turn rotations:








Multiplied by (1±i):






Divided by (1±i):




Indefinite integrals:






































Definite integrals:


Inverse functions:



























#44 Computer Math » PARI/GP code for Quaternions » 2024-01-22 08:41:54

lanxiyu
Replies: 0
{
my(
isreal=((x)->my(t=type(x));t=="t_INT"||t=="t_FRAC"||t=="t_REAL"),
isscalar=((x)->my(t=type(x));t=="t_INT"||t=="t_FRAC"||t=="t_REAL"||t=="t_COMPLEX"),
isquaternion=((x)->my(t=type(x));if(t=="t_COL"&&#x==4,for(i=1,4,if(!isreal(x[i]),return(0)));1,0)),
isvalid=((x)->isscalar(x)||isquaternion(x)),
toquaternion=((x)->if(isquaternion(x),x,isscalar(x),[real(x),imag(x),0,0],[])),
Qapply_=((f,x)->if(isscalar(x),f(x),isquaternion(x),my(v=x[^1],r=norml2(v)^(1/2),res=f(x[1]+I*r));concat(real(res),imag(res)*if(r,v/r,[1,0,0]~)),error("invalid type in Qapply")))
);
Qabs=((x)->if(isscalar(x),abs(x),isquaternion(x),norml2(x)^(1/2),error("invalid type in Qabs")));
Qadd=((x,y)->if(isvalid(x)&&isvalid(y),algadd(,x,y),error("invalid type in Qadd")));
Qapply=Qapply_;
Qarg=((x)->if(isscalar(x),arg(x),isquaternion(x),arg(x[1]+I*norml2(x[^1])^(1/2)),error("invalid type in Qarg")));
Qconj=((x)->if(isscalar(x),conj(x),isquaternion(x),concat(x[1],-x[^1]),error("invalid type in Qconj")));
Qdivl=((x,y)->if(isvalid(x)&&isvalid(y),algdivl(,x,y),error("invalid type in Qdivl")));
Qdivr=((x,y)->if(isvalid(x)&&isvalid(y),algdivr(,x,y),error("invalid type in Qdivr")));
Qinv=((x)->if(isvalid(x),alginv(,x),error("invalid type in Qinv")));
Qmul=((x,y)->if(isvalid(x)&&isvalid(y),algmul(,x,y),error("invalid type in Qmul")));
Qneg=((x)->if(isvalid(x),algneg(,x),error("invalid type in Qneg")));
Qpoleval=((T,x)->if(isvalid(x),algpoleval(,T,x),error("invalid type in Qpoleval")));
Qpow=((x,y)->if(type(y)=="t_INT",if(isvalid(x),return(algpow(,x,y))),isscalar(x)&&isscalar(y),return(x^y),isreal(y),if(isvalid(x),return(Qapply_((x)->x^y,x))),isreal(x),if(isvalid(y),return(Qapply_((y)->x^y,y))));error("invalid type in Qpow"));
Qreal=((x)->if(isscalar(x),real(x),isquaternion(x),x[1],error("invalid type in Qreal")));
Qsign=((x)->if(isreal(x),sign(x),isvalid(x),if(x,x/norml2(x)^(1/2),0*x),error("invalid type in Qsign")));
Qslerp=((x,y,t)->if(isvalid(x)&&isvalid(y)&&isreal(t),if(t===0,x,t===1,y,if(norml2(x)<norml2(y),[x,y,t]=[y,x,1-t]);algmul(,x,Qapply_((x)->x^t,algdivl(,x,y)))),error("invalid type in Qslerp")));
Qslerpinv=((x,y,z)->x=toquaternion(x);y=toquaternion(y);z=toquaternion(z);if(x==[]||y==[]||z==[],error("invalid type in Qslerpinv"));my(a,b,c,d,na,nb,nc,nx,nx2);nx2=norml2(x);nx=sqrt(nx2);na=x*y~;nb=x*z~;a=x*(na/nx2);b=x*(nb/nx2);c=y-a;d=z-b;na/=nx;nb/=nx;nc=sqrt(norml2(c));arg(nb+I*if(nc,(c*d~)/nc,sqrt(norml2(d))))/arg(na+nc*I));
Qsqr=((x)->if(isvalid(x),algsqr(,x),error("invalid type in Qsqr")));
Qsub=((x,y)->if(isvalid(x)&&isvalid(y),algsub(,x,y),error("invalid type in Qsub")));
}

#45 Computer Math » Mathematica implementation of matrix functions » 2024-01-21 17:31:12

lanxiyu
Replies: 0
(* Differentiable function *)
MatrixSqrt[m_] := MatrixPower[m, 1/2]
MatrixSin[m_] := (MatrixExp[I*m]-MatrixExp[-I*m])/(2*I)
MatrixCos[m_] := (MatrixExp[I*m]+MatrixExp[-I*m])/2
MatrixTan[m_] := -I*(MatrixExp[I*m]-MatrixExp[-I*m]).Inverse[MatrixExp[I*m]+MatrixExp[-I*m]]
MatrixCot[m_] := I*(MatrixExp[I*m]+MatrixExp[-I*m]).Inverse[MatrixExp[I*m]-MatrixExp[-I*m]]
MatrixSec[m_] := Inverse[MatrixCos[m]]
MatrixCsc[m_] := Inverse[MatrixSin[m]]
MatrixSinh[m_] := (MatrixExp[m]-MatrixExp[-m])/2
MatrixCosh[m_] := (MatrixExp[m]+MatrixExp[-m])/2
MatrixTanh[m_] := (MatrixExp[m]-MatrixExp[-m]).Inverse[MatrixExp[m]+MatrixExp[-m]]
MatrixCoth[m_] := (MatrixExp[m]+MatrixExp[-m]).Inverse[MatrixExp[m]-MatrixExp[-m]]
MatrixSech[m_] := Inverse[MatrixCosh[m]]
MatrixCsch[m_] := Inverse[MatrixSinh[m]]
(* From polar decomposition *)
MatrixSign[m_] := Module[{u,s,v},{u,s,v}=SingularValueDecomposition[m];u.ConjugateTranspose[v]]

#46 Formulas » Cubic theta functions » 2024-01-05 15:30:21

lanxiyu
Replies: 0

Definitions:




Specific values:











































































Transformations of the second order:






Transformations of the third order:






Transformations of the fourth order:






Other transformations:




























Related to Eisenstein series:


Euler q-series representations:


#47 Formulas » General form of Dixon elliptic functions » 2024-01-01 20:34:25

lanxiyu
Replies: 1

Specific values:

With Λ=nλ(α)+n'λ'(α)+n''λ''(α):

Differential equations:

Indefinite integrals:

Definite integrals:

Identities:

Hypergeometric series representation:

Limit on branch cut:

Opposite angle formula:

Periodicity: with Λ=nλ(α)+n'λ'(α)+n''λ''(α):

Translation by one-third periods:

Addition theorems:

Double angle formulas:

Transformations:

Legendre's relation:

Weierstrass elliptic function representations:

Dedekind eta function representations:

Equianharmonic (α=0) case:

Degenerate cases:

See On the doubly periodic functions arising out of the curve x³+y³-3αxy=1, Cubic theta functions, Cubics in Desmos

#48 Formulas » Identities of probability theory » 2023-12-18 09:57:58

lanxiyu
Replies: 0

Specific values:



Inequalities:


Complement rule:

Addition rule:




Multiplication rule:


Conditions:


Pairwise Independence does not imply Independence

#50 Formulas » Properties of limits and bounds » 2023-12-05 19:18:40

lanxiyu
Replies: 0

Limit on branch cut (elementary functions):
























Limit on branch cut (Bessel functions):












Limit on branch cut (Gauss hypergeometric function):


Limit on branch cut (elliptic integrals):










Limit on branch cut (inverse J-invariant):


Limit on branch cut (dilogarithm):


Triangle inequality:

Ball arithmetic:














Probability distribution:







https://math.stackexchange.com/questions/847266/

Board footer

Powered by FluxBB