Respuesta :

valmc

Answer:

law of cosines

c^2=(5)^2+(12)^2-2(5)(12)cos72

s1752891

Answer:

i had this question before

Step-by-step explanation:

c^2=a^2+b^2-2abcos(c)

c=sqrt(a^2+b^2-2abcos(c))

c=sqrt((5)^2+(12)^2-2(5)(12)cos(72))

c=sqrt(25+144-120cos(72))

c=sqrt(169-120cos(72))

c=sqrt(169-37.08)

c=sqrt(131.92)

c=11.49