Question 288700
What grade is this? Have you seen the Cosine Law before?


The Cosine Law is:

{{{c^2=a^2+b^2-2abCos(0)}}}


To find the smallest angle, o, we need to use c as the smallest side, 9.5. Plug the numbers in with a=12.8, b=13.7 and c=9.5, then solve for the angle, o.


{{{(9.5)^2=(12.8)^2+(13.7)^2-2(12.8)(13.7)Cos(o)}}}


Rearrange this equation to find:

{{{Cos(o) = -261.28/-350.72}}}
o=41.84 degrees


If you need any clarifications about steps in this problem, let me know!