... arccos 505 16 3 10 1 11 B := arccos 5555 56 11 C := arccos 275 p := 11 S := + + 11 + 10 1 10 1 11 + + 2 10 1 11 + + 2 10 1 11 + 10 1 ( 1/ 2 ) > expand(%); ... t1: =12 9/29+2/29*27 61^ (1/ 2);t2: =12 9/292/29*27 61^ (1/ 2);x1:=3*t1;y1:=-6*t1+5;z1:=9/2*t17/2;x2:=3*t2;y2:=-6*t2+5;z2:=9/2*t2-7/2; t1 := 12 9 27 61 + 29 29 t2 := 12 9 27 61 29 29 x1 := 387 27 61 + 29 29 y1 := 629 12 ... solve({f(2 ,1, -3),f(3,5,6),f(5,-4,-7),f(9,0 ,1) }); 577 -355 15 9 - 214 2 {b = ,c= ,a= ,d= } 13 13 13 13 > x^2+y^2+z^2 +15 9 /13 *x+577 /13 *y-355 /13 *z- 214 2 /13 =0; 15 9 577 355 214 2 x + y + z2 + x+ y z =0 13 13 13 13 2.5.9 Tính số yếu tố tam...