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# Trigonometric

## Introduction to Trigonometric

- MACSYMA has many Trig functions defined. Not all Trig identities are programmed, but it is possible for the user to add many of them using the pattern matching capabilities of the system. The Trig functions defined in MACSYMA are: ACOS, ACOSH, ACOT, ACOTH, ACSC, ACSCH, ASEC, ASECH, ASIN, ASINH, ATAN, ATANH, COS, COSH, COT, COTH, CSC, CSCH, SEC, SECH, SIN, SINH, TAN, and TANH. There are a number of commands especially for handling Trig functions, see TRIGEXPAND, TRIGREDUCE, and the switch TRIGSIGN. Two SHARE packages extend the simplification rules built into MACSYMA, NTRIG and ATRIG1. Do DESCRIBE(cmd) for details.

## Definitions for Trigonometric

Function: ACOS
  - Arc Cosine

Function: ACOSH
  - Hyperbolic Arc Cosine

Function: ACOT
  - Arc Cotangent

Function: ACOTH
  - Hyperbolic Arc Cotangent

Function: ACSC
  - Arc Cosecant

Function: ACSCH
  - Hyperbolic Arc Cosecant

Function: ASEC
  - Arc Secant

Function: ASECH
  - Hyperbolic Arc Secant

Function: ASIN
  - Arc Sine

Function: ASINH
  - Hyperbolic Arc Sine

Function: ATAN
  - Arc Tangent

Function: ATAN2 (Y,X)
  yields the value of ATAN(Y/X) in the interval -%PI to %PI.

Function: ATANH
  - Hyperbolic Arc Tangent

Function: ATRIG1
  - SHARE1;ATRIG1 FASL contains several additional simplification rules for inverse trig functions. Together with rules already known to Macsyma, the following angles are fully implemented: 0, %PI/6, %PI/4, %PI/3, and %PI/2. Corresponding angles in the other three quadrants are also available. Do LOAD(ATRIG1); to use them.

Function: COS
  - Cosine

Function: COSH
  - Hyperbolic Cosine

Function: COT
  - Cotangent

Function: COTH
  - Hyperbolic Cotangent

Function: CSC
  - Cosecant

Function: CSCH
  - Hyperbolic Cosecant

Variable: HALFANGLES
  default: [FALSE] - if TRUE causes half-angles to be simplified away.

Function: SEC
  - Secant

Function: SECH
  - Hyperbolic Secant

Function: SIN
  - Sine

Function: SINH
  - Hyperbolic Sine

Function: TAN
  - Tangent

Function: TANH
  - Hyperbolic Tangent

Function: TRIGEXPAND (exp)
  expands trigonometric and hyperbolic functions of sums of angles and of multiple angles occurring in exp. For best results, exp should be expanded. To enhance user control of simplification, this function expands only one level at a time, expanding sums of angles or multiple angles. To obtain full expansion into sines and cosines immediately, set the switch TRIGEXPAND:TRUE. TRIGEXPAND default: [FALSE] - if TRUE causes expansion of all expressions containing SINs and COSs occurring subsequently. HALFANGLES[FALSE] - if TRUE causes half-angles to be simplified away. TRIGEXPANDPLUS[TRUE] - controls the "sum" rule for TRIGEXPAND, expansion of sums (e.g. SIN(X+Y)) will take place only if TRIGEXPANDPLUS is TRUE. TRIGEXPANDTIMES[TRUE] - controls the "product" rule for TRIGEXPAND, expansion of products (e.g. SIN(2*X)) will take place only if TRIGEXPANDTIMES is TRUE.

      (%i1) X+SIN(3*X)/SIN(X),TRIGEXPAND=TRUE,EXPAND;
                                    2           2
      (%o1)                     - SIN (X) + 3 COS (X) + X
      (%i2) TRIGEXPAND(SIN(10*X+Y));
      (%o2)               COS(10 X) SIN(Y) + SIN(10 X) COS(Y)

Variable: TRIGEXPANDPLUS
  default: [TRUE] - controls the "sum" rule for TRIGEXPAND. Thus, when the TRIGEXPAND command is used or the TRIGEXPAND switch set to TRUE, expansion of sums (e.g. SIN(X+Y)) will take place only if TRIGEXPANDPLUS is TRUE.

Variable: TRIGEXPANDTIMES
  default: [TRUE] - controls the "product" rule for TRIGEXPAND. Thus, when the TRIGEXPAND command is used or the TRIGEXPAND switch set to TRUE, expansion of products (e.g. SIN(2*X)) will take place only if TRIGEXPANDTIMES is TRUE.

Variable: TRIGINVERSES
  default: [ALL] - controls the simplification of the composition of trig and hyperbolic functions with their inverse functions: If ALL, both e.g. ATAN(TAN(X)) and TAN(ATAN(X)) simplify to X. If TRUE, the arcfunction(function(x)) simplification is turned off. If FALSE, both the arcfun(fun(x)) and fun(arcfun(x)) simplifications are turned off.

Function: TRIGREDUCE (exp, var)
  combines products and powers of trigonometric and hyperbolic SINs and COSs of var into those of multiples of var. It also tries to eliminate these functions when they occur in denominators. If var is omitted then all variables in exp are used. Also see the POISSIMP function (6.6).

      (%i4) TRIGREDUCE(-SIN(X)^2+3*COS(X)^2+X);
      (%o4)                        2 COS(2 X) + X + 1
      The trigonometric simplification routines will use declared
      information in some simple cases.  Declarations about variables are
      used as follows, e.g.
      (%i5) DECLARE(J, INTEGER, E, EVEN, O, ODD)$
      (%i6) SIN(X + (E + 1/2)*%PI)$
      (%o6)                      COS(X)
      (%i7) SIN(X + (O + 1/2) %PI);
      (%o7)                     - COS(X)

Variable: TRIGSIGN
  default: [TRUE] - if TRUE permits simplification of negative arguments to trigonometric functions. E.g., SIN(-X) will become -SIN(X) only if TRIGSIGN is TRUE.

Function: TRIGSIMP (expr)
  employs the identities sin(x)^2 + cos(x)^2 = 1 and cosh(x)^2 - sinh(x)^2 = 1 to simplify expressions containing tan, sec, etc. to sin, cos, sinh, cosh so that further simplification may be obtained by using TRIGREDUCE on the result. Some examples may be seen by doing DEMO("trgsmp.dem"); . See also the TRIGSUM function.

Function: TRIGRAT (trigexp)
  gives a canonical simplifyed quasilinear form of a trigonometrical expression; trigexp is a rational fraction of several sin, cos or tan, the arguments of them are linear forms in some variables (or kernels) and %pi/n (n integer) with integer coefficients. The result is a simplifyed fraction with numerator and denominator linear in sin and cos. Thus TRIGRAT linearize always when it is possible.(written by D. Lazard).

      (%i1) trigrat(sin(3*a)/sin(a+%pi/3));

      (%o1) 		        sqrt(3) sin(2 a) + cos(2 a) - 1

  Here is another example (for which the function was intended); see [Davenport, Siret, Tournier, Calcul Formel, Masson (or in english, Addison-Wesley), section 1.5.5, Morley theorem). Timings are on VAX 780.

      (%i4)   c:%pi/3-a-b;

      					   %pi
      (%o4) 				 - b - a + ---
      					    3

      (%i5)   bc:sin(a)*sin(3*c)/sin(a+b);

      			     sin(a) sin(3 b + 3 a)
      (%o5) 			     ---------------------
      				  sin(b + a)

      (%i6)   ba:bc,c=a,a=c$

      (%i7)   ac2:ba^2+bc^2-2*bc*ba*cos(b);

      	2       2
           sin (a) sin (3 b + 3 a)
      (%o7) -----------------------
      	      2
      	   sin (b + a)

      					%pi
         2 sin(a) sin(3 a) cos(b) sin(b + a - ---) sin(3 b + 3 a)
      					 3
       - --------------------------------------------------------
      			   %pi
      		   sin(a - ---) sin(b + a)
      			    3

            2	        2	  %pi
         sin (3 a) sin (b + a - ---)
      			   3
       + ---------------------------
      	     2	   %pi
      	  sin (a - ---)
      		    3

      (%i9)   trigrat(ac2);
      Totaltime= 65866 msec.  GCtime= 7716 msec.

      (%o9)
      - (sqrt(3) sin(4 b + 4 a) - cos(4 b + 4 a)

      - 2 sqrt(3) sin(4 b + 2 a)

      + 2 cos(4 b + 2 a) - 2 sqrt(3) sin(2 b + 4 a) + 2 cos(2 b + 4 a)

      + 4 sqrt(3) sin(2 b + 2 a) - 8 cos(2 b + 2 a) - 4 cos(2 b - 2 a)

      + sqrt(3) sin(4 b) - cos(4 b) - 2 sqrt(3) sin(2 b) + 10 cos(2 b)

      + sqrt(3) sin(4 a) - cos(4 a) - 2 sqrt(3) sin(2 a) + 10 cos(2 a)

         - 9)/4

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