cosA= BA^2+AC^2-BC^2/2AB*AC=49+81-64/14*9=66/126
cosB=AB^2+BC^2-AC^2/2AB*BC=49+64-81/14*8=32/112
cosC=BC^2+AC^2-AB^2/2BC*AC=64+81-49/16*9=96/144
cosA= BA^2+AC^2-BC^2/2AB*AC=49+81-64/14*9=66/126
cosB=AB^2+BC^2-AC^2/2AB*BC=49+64-81/14*8=32/112
cosC=BC^2+AC^2-AB^2/2BC*AC=64+81-49/16*9=96/144