Ta có:

cosA=b2+c2a22bc=852+54252,122.85.540,81

=> cosA=b2+c2a22bc=852+54252,122.85.540,81

A^36

cosB=a2+c2b22ac=52,12+5428522.52,1.540,28

=> B^10628

=> C=C^=180A^B^=1803610628=3732