( a/sinA )= (c/sinC )
(=) (5/ sinA ) = (12/sin37° )
=) sinA= (5.sin37°)/12 = 0,251
=) góc A ~ 14°31’
Ta có: Góc C= 180°-14°31’-37°= 128°29’
Ta có: b²= 5²+12²-2.5.12.cos128°29’= 243,67
√b = 15,61
Diện tícj tam giác ABC = ½.ab.sinC=½.12.15,61.sin37°= 56,367