
/*
trigtools  package for working with expressions with trigonometric and hyperbolic functions.
version 1.01,  2013.11
Copyright (C)  A.Domarkas 2013
rigtools package is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License.
*/

/*
The function c2sin convert expression a*cos(x)+b*sin(x)  to r*sin(x+phi).
*/

c2sin(f):=block([x,a,b,r,phi],
x:listofvars(f)[1],
a:coeff(f,cos(x)),b:coeff(f,sin(x)),
r:signum(b)*sqrt(a^2+b^2),
phi:atan(a/b),
r*sin(x+phi)
)$

/*
The function c2cos convert expression a*cos(x)+b*sin(x)  to r*cos(x-phi).
*/

c2cos(f):=block([x,a,b,r,phi],
x:listofvars(f)[1],
a:coeff(f,sin(x)),b:coeff(f,cos(x)),
r:signum(b)*sqrt(a^2+b^2),
phi:atan(a/b),
r*cos(x-phi))$

/*
The function c2trig (convert to trigonometric) reduce expression with hyperbolic functions
 sinh, cosh, tanh, coth to trigonometric expression with sin, cos, tan, cot.
*/

c2trig(r):=block([x,i,sinv,cosv,mi,mii,%iargs:false],
mi(x):=%i*x,
mii(x):=-%i*x,
sinv:compose_functions([mii,sin,mi]),
tanv:compose_functions([mii,tan,mi]),
cosv:compose_functions([cos,mi]),
cotv:compose_functions([mi,cot,mi]),
subst([sinh=sinv,cosh=cosv,tanh=tanv,coth=cotv],r),
subst(%i=i,%%),
trigrat(%%),
trigreduce(%%),
subst(i=%i,%%)
)$

/*
The function c2hyp (convert to hyperbolic) convert expression with exp function
 to expression with hyperbolic functions sinh, cosh.
*/

c2hyp(expr):=block([pa,f,e1,e2,S],
pa(f):=if atom(f) then f else makelist(part(f,k),k,1,length(f)),
S:[],
e1:[pa(expr)],
e2:sublist(%%,listp),
sublist(e2,lambda ([x], part(x,1)=%e)),
S:append(S,%%),
e1:flatten(e2),
while e1#[] do
(map(pa,e1),
e2:sublist(%%,listp),
sublist(e2,lambda ([x], part(x,1)=%e)),
S:append(S,%%),
e1:flatten(e2)),
makelist(exp(S[k][2])=cosh(S[k][2])+sinh(S[k][2]),k,1,length(S)),
subst(%%,expr)
)$

/*
The function trigfactor factors expressions of form  +-sin(x)+-cos(y)
*/

trigfactor(f):=block([r,_x,_y,%piargs:false],
st(f):=block([f0,fun,a1],
       f0:part(f,0),
       if f0=sin or f0=cos then return([part(f,0),part(f,1)])
       elseif f0="-" then
       f0:part(f,1,0),
       if f0=sin or f0=cos then
       return([part(f,1,0),part(f,1,1)])
       else fail
       ),
          cx(x):=%pi/2-x,
if nterms(f)=2 and op(f)="+" then
(s1:st(part(f,1))[1], s2:st(part(f,2))[1])
else return(f),
if s1#false and f2#false and s1#s2 then
         (sinv:compose_functions([cos,cx]),f1:subst([sin=sinv],f))
         else f1:f,
_x:st(part(f1,1))[2],_y:st(part(f1,2))[2],
r:[2*sin((_x+_y)/2)*cos((_x-_y)/2),2*sin((_x-_y)/2)*cos((_x+_y)/2),
2*cos((_x+_y)/2)*cos((_x-_y)/2),2*sin((_x+_y)/2)*sin((_x-_y)/2)],
r:append(r,-r),
%piargs:true,
sublist(r,lambda([x],trigrat(f1-x)=0)),
expand(%%),
if length(%%)>=1 then %%[1] else f )$

/*
The function trigsolve find solutions of trigonometric equation from interval [a, b).
*/

trigsolve(eq,a,b):=block([s,i,ats,algebraic],
algebraic:true,
to_poly_solve([eq], [x],'simpfuncs =
['rootscontract,'expand,'radcan,'nicedummies]),
s:makelist(rhs(part(%%,k)[1]),k,1,length(%%)),
ats:[],
for i:1 thru length(s) do 
(makelist(ev(s[i],%z0=k),k,-10,10),
ats:append(ats,%%)),
sublist(ats,lambda([e],e>=a and e<b)),
sort(%%),
setify(%%)
)$

/*
The function trigvalue compute values of sin(m*pi/n), cos(m*pi/n), tan(m*pi/n), cot(m*pi/n) in radicals.
*/

trigvalue(r):=block(
[f,x,sol,spr,spr1,solvetrigwarn,algebraic],
load (sqdnst),
solvetrigwarn:false,
algebraic:true,
if freeof(%pi,r) then return(r),
f:part(r,0),
if part(r,0)="-" then f:part(r,1,0),
if f=cot then f:tan,
sol:solve(x=r,%pi)[1],
sol*denom(rhs(sol)),
map(f,%%),
trigexpand(%%),
factor(%%),
spr:solve(%%,x),
if (length(spr)<=2 or not freeof(%i,%%)) then return(r),
spr1:sublist(spr,lambda([e],is(abs(rhs(e)-r)<ratepsilon))),
if %%=[] then return(r),
rhs(spr1[1]),
sqrtdenest(%%),
factor(%%)
)$

/*
The function trigeval compute values of expressions with sin(m*pi/n), cos(m*pi/n), tan(m*pi/n), cot(m*pi/n)
in radicals.
*/

trigeval(r):=block([sinv,cosv,tanv,cotv],
sinv:compose_functions([trigvalue,sin]),
cosv:compose_functions([trigvalue,cos]),
tanv:compose_functions([trigvalue,tan]),
cotv:compose_functions([trigvalue,cot]),
subst([sin=sinv,cos=cosv, tan=tanv,cot=cotv],r)
)$

/*
The function atan_contract contracts atan functions.
*/

atan_contract(r):=block([],
if equal(r,%pi/2) then return(%pi/2)
elseif equal(r,-%pi/2) then return(-%pi/2),
is(abs(r)<%pi/2),
if %%=true then
(
tan(r),
trigexpand(%%),
trigexpand(%%),
atan(%%)
)
else return(r)
)$

/*
compose_functions -- function from to_poly_solve package( used for trigeval, c2trig)
*/

compose_functions(l):=block([z,f],
if listp(l) then (l:reverse(l),f:z,for lk in l do 
f:funmake(lk,[f]),buildq([z,f],lambda([z],f))) else 
error("The argument to 'compose_functions' must be a list."))$

