URAL 1294. Mars Satellites (cosine theorem math ah)

Title Link: http://acm.timus.ru/problem.aspx?space=1&num=1294

1294. Mars Satellitestime limit:1.0 Second
Memory limit:64 MB
Four artificial satellites travel in one plane along the areostationary orbit around Mars. They has code names A, B, C and D and travel exactly in the this order. Venus ' s Scouts for military purposes (for-what particular purpose they do not say) decided to find a distance between sat Ellites C and D. All Mars satellites could measure distances to the other satellites, that's why all-what's needed to do are to penetrate In the computer system of satellite C and measure, the distance to satellite D (or vice versa). Nevertheless, Martians is not so stupid and has not very bad defense. That's why all could Venus's scouts do are to break the defense of satellites A and B (that were older models). They measured distances from satellites A and B to satellites C and D, but now they does not know how to find the distance F Rom C to D using these measurements. You can help them. Inputthere is 4 numbers:distances from a to D, from A to C, from B to D and from B to C in thousands kilometers (intEgers from 1 to 10000). Satellites can measure distance even through the planet and you may assume that orbit is a circle. Assume the radius of the orbit equal to 20392 miles as it should is for the real areostationary orbit. Outputif It is impossible-find out the distance from C to D with these data, you should print "impossible.", otherwise You ' to ' print ' Distance is x miles. ', where X is the required Distance in kilometers (rounded to the integer number). Sample

input	Output
4 7 5 7	Distance is 5385 miles.

Test instructions

In a circle there is a fixed order of four points, tell you the distance of the ad AC BD BC, the distance to the CD!

Ps:

Equal to the central angle of equal chord in the same circle

The code is as follows:

#include <cstdio> #include <cmath>//equal to the central angle of equal chord in the same circle int main () {    int ad, AC, BD, BC;    while (~SCANF ("%d%d%d%d", &AD,&AC,&BD,&BC))    {        if (Ad*ac = = BD*BC)//denominator equal, subtract to zero        {            printf ("impossible.\n");            Continue;        }        Cosine theorem Simplification:        double t1 = (AD*AD+AC*AC) *2.0*bd*bc-(BD*BD+BC*BC) *2.0*ad*ac;        Double t2 = 2*bd*bc-2*ad*ac;        Double tt = T1*1.0/T2;        if (TT < 0)        {            printf ("impossible.\n");        }        else        {            tt = sqrt (TT);            printf ("Distance is%.0LF km.\n", tt*1000);        }    }    return 0;}

URAL 1294. Mars Satellites (cosine theorem math ah)