Zoj 1090 three-point circumference

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// 1090 mathematical questions
// Obtain the circumference of the circle determined by the three points.
// First use the cosine theorem cos α = (B ^ 2 + C ^ 2-A ^ 2)/(2bc) and then calculate sin α, then the diameter d = A/sin α, perimeter L = D π
# Include <iostream>
# Include <iomanip>
# Include <math. h>
Using namespace STD;
# Define PI 3.141592653589793

 

Int main ()
{
Double X1, Y1, X2, Y2, X3, Y3;
Double wer1, wer2, wer3;
Double A, B, C;
While (CIN> x1> Y1> X2> Y2> X3> Y3 )! = 0)
{
Wer1 = POW (x1-x2), 2) + POW (y1-y2), 2 );
A = SQRT (wer1 );
Wer2 = POW (x3-x2), 2) + POW (y3-y2), 2 );
B = SQRT (wer2 );
Wer3 = POW (x1-x3), 2) + POW (y1-y3), 2 );
C = SQRT (wer3 );
Double ans;
Ans = (B * B + C * C-A * A)/(2 * B * C );
Ans = SQRT (1-ans * ans );
Ans = A * PI/ANS;
Cout <setiosflags (IOs: fixed) <setprecision (2) <ans <Endl;
}
Return 0;
}