Respuesta :

a=4,
b=3,
c= 2

a² + b² -2abcosC =c²
a² + b² - c² = 2abcosC
2abcosC = 4² + 3² -2² = 16 + 9-4= 21

Answer : B.21
The equation can be solved for 2abcosC
a²+b²-c² = 2abcosC
4²+3²-2² = 2abcosC
16 + 9 - 4 = 2abcosC
25 - 4 = 2abcosC
21 = 2abcosc