Question 1180986
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Use the Cosine Law.



Or, alternatively, calculate the area of the triangle using the Heron's formula;


Then use another formula for the triangle area  S = {{{(1/2)*a*b*sin(gamma)}}}, where "a" and "b" are any two sides 

and {{{gamma}}} is the included angle.
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You are instructed - hence, you know the way.


The rest is on you.