// orthocenter-isoscel-ex70.ggb 44s, 35.4s, 29s, 17.7s,15.74s, 13.64, 12.2s, 11.11s
//[v5^4*v3^2+2*v5^2*v6^2*v3^2+v6^4*v3^2-2*v5^3*v3^3-2*v5*v6^2*v3^3+v5^2*v3^4+v6^2*v3^4-2*v5^2*v6*v3^2*v4-2*v6^3*v3^2*v4+v5^4*v4^2+2*v5^2*v6^2*v4^2+v6^4*v4^2-2*v5^3*v3*v4^2-2*v5*v6^2*v3*v4^2+2*v5^2*v3^2*v4^2+2*v6^2*v3^2*v4^2-2*v5^2*v6*v4^3-2*v6^3*v4^3+v5^2*v4^4+v6^2*v4^4]
//aa:=gbasis([2*v7+-1*v3,2*v8+-1*v4,2*v9+-1*v5,2*v10+-1*v6,-1*v12+v10+-1*v5,-1*v11+v9+v6,-1*v14+v8+v3,-1*v13+v7+-1*v4,v15*v12+-1*v16*v11+-1*v15*v10+v11*v10+v16*v9+-1*v12*v9,v15*v14+-1*v16*v13+-1*v15*v8+v13*v8+v16*v7+-1*v14*v7,v17*v14+-1*v18*v13+-1*v17*v8+v13*v8+v18*v7+-1*v14*v7,-1*v18^2+-1*v17^2+2*v18*v16+2*v17*v15,v19*v12+-1*v20*v11+-1*v19*v10+v11*v10+v20*v9+-1*v12*v9,-1*v20^2+-1*v19^2+2*v20*v16+2*v19*v15,-1*v21*v4+v22*v3,v21*v20+-1*v22*v19+-1*v21*v18+v19*v18+v22*v17+-1*v20*v17,v23*v6+-1*v24*v5,v23*v20+-1*v24*v19+-1*v23*v18+v19*v18+v24*v17+-1*v20*v17,-1+v27*v24^2+v27*v23^2+-1*v27*v22^2+-1*v27*v21^2],[v7,v8,v9,v10,v11,v12,v13,v14,v15,v16,v17,v18,v19,v20,v21,v22,v23,v24,v27]);
aa:=eliminate([2*v7+-1*v3,2*v8+-1*v4,2*v9+-1*v5,2*v10+-1*v6,-1*v12+v10+-1*v5,-1*v11+v9+v6,-1*v14+v8+v3,-1*v13+v7+-1*v4,v15*v12+-1*v16*v11+-1*v15*v10+v11*v10+v16*v9+-1*v12*v9,v15*v14+-1*v16*v13+-1*v15*v8+v13*v8+v16*v7+-1*v14*v7,v17*v14+-1*v18*v13+-1*v17*v8+v13*v8+v18*v7+-1*v14*v7,-1*v18^2+-1*v17^2+2*v18*v16+2*v17*v15,v19*v12+-1*v20*v11+-1*v19*v10+v11*v10+v20*v9+-1*v12*v9,-1*v20^2+-1*v19^2+2*v20*v16+2*v19*v15,-1*v21*v4+v22*v3,v21*v20+-1*v22*v19+-1*v21*v18+v19*v18+v22*v17+-1*v20*v17,v23*v6+-1*v24*v5,v23*v20+-1*v24*v19+-1*v23*v18+v19*v18+v24*v17+-1*v20*v17,-1+v27*v24^2+v27*v23^2+-1*v27*v22^2+-1*v27*v21^2],revlist([v7,v8,v9,v10,v11,v12,v13,v14,v15,v16,v17,v18,v19,v20,v21,v22,v23,v24,v27]))