gaokao 2015 Q12

gaokao · China · fujian-science Sine and Cosine Rules Find a side length using the cosine rule

12. If the area of acute triangle $A B C$ is $10 \sqrt { 3 }$, and $A B = 5$, $A C = 8$, then $B C$ equals $\_\_\_\_$.

12. If the area of acute triangle $A B C$ is $10 \sqrt { 3 }$, and $A B = 5$, $A C = 8$, then $B C$ equals $\_\_\_\_$.