TMatixDは行列を扱う

{
gROOT->Reset();


TMatrixD m(3,3);

m[0][0] = 1.0;
m[0][1] = 2.0;
m[0][2] = 3.0;

m[1][0] = 4.0;
m[1][1] = 8.0;
m[1][2] = 6.0;

m[2][0] = 7.0;
m[2][1] = 8.0;
m[2][2] = 9.0;

Double_t det;
m.Invert(&det);

m.Print();

}