Question 1070832
Use the law of cosines,
{{{b^2=a^2+c^2-2ac*cos(B)}}}
{{{cos(B)=(b^2-a^2-c^2)/(2ac)}}}
{{{cos(B)=(17.7^2-13.2^2-5.5^2)/(2(13.2)(5.5))}}}