How to calculate degree ?

You are denying what is right in front of your face. If you cannot create a corrolation between two different units of measurement, how can you create a forex chart using time and price ? How can you write code to draw indicator lines on such meaningless values ?

When you calculate the angle you are not saying what is the angle of going 5 miles in 10 minutes, you are saying what is the angle of the line on the chart you have created, reletive to its x axis. 

The math can be applied to any two sets of values that you wish to corrolate on a chart, regardless of their units of measurement. I did not invent the math it is established and proven.

Of course the angle changes if you mess with the scale. Calculate the angle from a point 10 feet down your yard to the apex of your house. Now change that to 10 meters down your yard. Is it impossible to calculate an angle from a point in your yard to the apex of your house, just because it is possible to change the scale ?  What happens when you change the scale on your forex chart from 1hr to 4hr, the whole chart is different, does that make it meaningless ?

From Wikipedia:

The slope of a line in the plane containing the x and y axes is generally represented by the letter m, and is defined as the change in the y coordinate divided by the corresponding change in the x coordinate, between two distinct points on the line. 

The angle θ between -90° and 90° that a line makes with the x-axis is related to the slope m as follows:

and

  (the inverse function of tangent).

For example, consider a line running through the points (2,8) and (3,20). This line has a slope, m, of

The angle θ between -90° and 90° that this line makes with the x axis is

https://forum.mql4.com/59930/page3

You are still wrong . . .  and angle is specified in units of arc,  be it degree or radians . . . or anything else . . .  but it does not specify the units of the measurements of the 2 lines that make the angle.  So given an angle we have to assume that the units of the 2 lines is the same,  we have no information to do otherwise. 

You think you proved me wrong because you asked a trick question on that other thread ? That is how the flat earth society make their case.

I guess I am going to have to write a script to prove this, I'll post it later.

OK Place a trendline on a chart. Name it "trend1" then run this script. You can move the line, zoom the chart etc then run it again. You will see I am not wrong.

//+------------------------------------------------------------------+
//|                                                        Angle.mq4 |
//|                                             Copyright 2014, SDC. |
//+------------------------------------------------------------------+
//| This script requires a trendline be already placed on the chart. |
//| the trendline should be named "trend1"                           |
//| Run the script and it will find the angle of that trendline      |
//| reletive to the x axis of the chart.                             |
//| To verify if the calculation is accurate, it will attempt to     |
//| place text at the same angle as the line.                        |
//| I used a trendline for convenience, the same code can be applied |
//| to any kind of a line with price time co-ordinates.              |
//+------------------------------------------------------------------+
#property copyright "Copyright 2014, SDC."
#property version   "1.00"
#property strict
input string name = "trend1"; //Name of the Trendline
//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
void OnStart()
  {
//---
   int x1=0,x2=0;
   int y1=0,y2=0;
   long chart = ChartGetInteger(0,CHART_HEIGHT_IN_PIXELS,0);
   long t1=ObjectGetInteger(0,name,OBJPROP_TIME,0);
   double p1=ObjectGetDouble(0,name,OBJPROP_PRICE,0);
   long t2=ObjectGetInteger(0,name,OBJPROP_TIME,1);
   double p2=ObjectGetDouble(0,name,OBJPROP_PRICE,1);
   ChartTimePriceToXY(0,0,t1,p1,x1,y1);
   ChartTimePriceToXY(0,0,t2,p2,x2,y2);
   int size = (int)chart;
   y1=size-y1;
   y2=size-y2;
   double angle =(MathArctan(((double)y2-(double)y1)/((double)x2-(double)x1))*180)/M_PI;
   string textangle = DoubleToStr(angle,1);
   string text = StringConcatenate("The Angle of This Line is ",textangle,"°");
   ObjectCreate(0,"sometext",OBJ_TEXT,0,0,0);
   ObjectSet("sometext",OBJPROP_TIME1,t1);
   ObjectSet("sometext",OBJPROP_PRICE1,p1);
   ObjectSetInteger(0,"sometext",OBJPROP_ANCHOR,ANCHOR_LEFT_LOWER);
   ObjectSetString(0,"sometext",OBJPROP_TEXT,text);
   ObjectSetDouble(0,"sometext",OBJPROP_ANGLE,angle);
   ObjectSet("sometext",OBJPROP_COLOR,clrAqua);
   ObjectSet("sometext",OBJPROP_FONTSIZE,18);
  }
//+------------------------------------------------------------------+

is it ?