Hi everyone!

I'm currently expering problems in a project of mine. I would like to
calculate the sinand cos for a angel. Delphi calculates the value in
radians. so far everythings works accodring to plan.
But I want to convert it to DEG. When I use the function RadToDeg the answer
returned doesn't match the value I get when calculating the Degree sin on a
ordinary calculator.

for example sin 45 degrees should be approx 0,707xxx. when calculated with
Delphi and then converted using RadToDeg I get an answer saying 30.xx

Can someone give me a clue on how to get around this problem?

Thank you on beforehand

Fredrik Tholander
Sweden

Hello Fredrik

You have to think different. (some smartass said that some time back,
can't remember who though :)

I think you're trying to do this (because you mention RadToDeg, which is
completely useless in this context):

X := RadToDeg(Sin(45));

The manuals are a little confusing here:

It says "returns the sine of the value X in radians", which can make
you think it returns a radian value if you read it a little too fast :)
However, Sin, Cos and Tan should only return values between 0.0 and 1.0
(according to my math teacher).

The right interpretation of the manuals is that you give the
function a radian angle, and it returns a value between 0 and 1:
X := Sin(DegToRad(45)); (returns 0.707*** which is correct!)

Happy hacking,
- David

David Skogvold answered already correctly. But let me mention here some
basic issue. Is it really necessary that in Delphi all needs a
prefabricated
procedure or function or a component even for the most primitive jobs?

Simply multiply the radians with 180/pi and you get the degrees and vice
versa.

Every 2 weeks there comes a mail from a C programmer, looking for the
power function in Pascal or Delphi. It is a similar primitive thing:
Power := Exp(ln(base) * ex);

It seems that Delphi is very very bound to "modern times"...

Franz Glaser

I had the same problem a while a go . i wrote these functions to solve it.

Steve Beaulieu
S...@Mediaone.net

{***************************************************************************
*  Radians    - converts degrees to radians                                *
*  Degrees    - converts radians to degrees                                *
*  CosD       - cosine in degrees                                          *
*  SinD       - sine in degrees                                            *
*  TanD       - tangent in degrees                                         *
*  CotD       - CoTangent in degrees                                       *
*  ArcTanD    - ArcTangent in degrees                                      *
*  Power      - power a^n                                                  *
*  DMS_TO_RAE - Converts two sets of lat lons                              *
*               to range azimuth and elevation                             *
****************************************************************************

Unit LatMath;

Interface

Const
  Ln10        = 2.30258509299405E+000;  { Ln( 10 )     =  2.3025651 }
  OneOverLn10 = 0.43429448190325E+000;  { 1 / Ln( 10 ) =  0.4342945 }
  PiOver180   = 1.74532925199433E-002;  { Pi / 180     =  0.0174533 }
  PiUnder180  = 5.72957795130823E+001;  { 180 / Pi     = 57.2957795 }

{**************************************************************************}

Function Power(Base : Real; Exponent : Integer) : Real;
Function SinD(Angle : Real) : Real;
Function ArcTanD(Angle : Real) : Real;
Function CotD(Angle : Real) : Real;
Function TanD(Angle : Real) : Real;
Function CosD(Angle : Real) : Real;
Function Degrees(Angle : Real) : Real;
Function Radians(Angle : Real) : Real;
Procedure DMS_To_RAE( VAR LatRef,LonRef,HightRef,
                          LatCase,LonCase,HightCase,
                          ToAZ,FromAz,Rng,El : Real );

Implementation

{***************************************************************************

Function Radians(Angle : Real) : Real;

  Begin
    Radians := Angle * PiOver180   { Angle * Pi / 180 }
  End;
{***************************************************************************

Function Degrees(Angle : Real) : Real;

  Begin
    Degrees := Angle * PiUnder180  { Angle * 180 / Pi }
  End;
{***************************************************************************

Function CosD(Angle : Real) : Real;

  Begin
    CosD := Cos( Radians( Angle ) )
  End;
{***************************************************************************

Function TanD(Angle : Real) : Real;

  Begin
    TanD := Sin( Radians( Angle ) ) / Cos( Radians( Angle ) )
  End;
{***************************************************************************

Function CotD(Angle : Real) : Real;

  Begin
    CotD := Cos( Radians( Angle ) ) / Sin( Radians( Angle ) )
  End;
{***************************************************************************

Function ArcTanD(Angle : Real) : Real;

  Begin
    ArcTanD := Degrees(ArcTan( Angle ))
  End;
{***************************************************************************

Function SinD(Angle : Real) : Real;

  Begin
    SinD := Sin( Radians( Angle ) )
  End;

{***************************************************************************

Function Power(Base : Real; Exponent : Integer) : Real;

  Var
    BPower : Real;
    t      : Integer;

  Begin
    If (Exponent = 0) Then
      Power := 1
    Else
      Begin
        BPower := 1.0;
        For t := 1 To Exponent Do
          BPower := BPower * Base;
        Power := BPower
      End
  End;

{***************************************************************************

{**************************************************************************}
{***************************************************************************
*  LatRef    = INPUT Latitude of Refferance site In Degrees                *
*  LonRef    = INPUT Longitude of Refferance site In Degrees               *
*  HightRef  = INPUT MSL of Refferance site In Feet                        *
*  LatCase   = INPUT Latitude of Case site In Degrees                      *
*  LonCase   = INPUT Longitude of Case site In Degrees                     *
*  HightCase = INPUT AGL of Case site In Feet                              *
*  RNG       = OUTPUT Distance in feet from reff site to case site         *
*  ToAz      = OUTPUT Azimuth in Degrees from reff site to case site       *
*  FromAz    = OUTPUT Azimuth in degrees from case sith to reff site       *
*  El        = OUTPUT  Elevation Angel from reff site                      *
*                      to case site (5/6 earth curve)                      *
****************************************************************************

Procedure DMS_To_RAE( VAR LatRef,LonRef,HightRef,
                          LatCase,LonCase,HightCase,
                          ToAZ,FromAz,Rng,El : Real );

Const
  Goof = 0.0000000001;

VAR
  LonDiff, TMP1, TMP2,
  LatRefmLatcaseD2,
  LatRefPLatcaseD2     : REAL;

Begin

  If LatRef = LatCase Then LatRef := LatRef + Goof;
  If LonRef = LonCase Then LonRef := LonRef + Goof;
  If LonCase >LonRef Then
    LonDiff := LonCase - LonRef
  Else
    LonDiff := LonRef - LonCase;
  LatRefmLatcaseD2 := (LatRef-LatCase)/2;
  LatRefPLatcaseD2 := (LatRef+LatCase)/2;
  Tmp1 :=  ArcTanD( CotD(LonDiff/2)*SinD(LatRefMLatcaseD2)
          /CosD(LatRefPLatcaseD2) );
  Tmp2 :=  ArcTanD( CotD(LonDiff/2)*CosD(LatRefMLatcaseD2)
          /SinD(LatRefPLatcaseD2) );
  If LonRef>LonCase Then
    Begin
     ToAz := (tmp2+tmp1);
     FromAz := 360 - (Tmp2 - Tmp1);
    End
  Else
   Begin
     ToAz := 360 - (Tmp2 + Tmp1);
     FromAz := (Tmp2 - Tmp1);
   End;

  Rng :=((ArcTanD( TanD(LatRefMLatcaseD2)*
              SinD(tmp2)/SinD(tmp1)))*2)*60.00*6076.1;

  EL := ArcTanD(((HightCase-HightRef)-
            ((Power(RNG/6076.1,2)*5)/6))/(RNG));

End;
(***************************************************************************
**)

End.