Area of a triangle in language Pascal

Language

Pascal
Description

Write a program that prompts the user to enter the tree points (x1, y1), (x2, y2), and (x3, y3) of a triangle and displays its area.
The formula for computing the area of a triangle is:
s = (side1 + side2 + side3) / 2
area = sqrt(s * (s - side1) * (s - side2) * (s - side3))

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program AreaOfATriangle;

uses crt, math;

var area, s, side1, side2, side3 : real;

var x1, x2, x3, y1, y2 : real;

var y3 : real;

begin

    write ('Enter the value of x1: ');

    readln (x1);

    write ('Enter the value of x2: ');

    readln (x2);

    write ('Enter the value of x3: ');

    readln (x3);

    write ('Enter the value of y1: ');

    readln (y1);

    write ('Enter the value of y2: ');

    readln (y2);

    write ('Enter the value of y3: ');

    readln (y3);

    side1 := sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));

    side2 := sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));

    side3 := sqrt((x3-x1)*(x3-x1)+(y3-y1)*(y3-y1));

    s := (side1+side2+side3)/2;

    area := sqrt(s*(s-side1)*(s-side2)*(s-side3));

    writeln ('Value of area: ', area:0:6);

    writeln ('Value of s: ', s:0:6);

    writeln ('Value of side1: ', side1:0:6);

    writeln ('Value of side2: ', side2:0:6);

    writeln ('Value of side3: ', side3:0:6);

    writeln;

    write ('Press any key to finish . . . ');

    readkey;

end.