To answer this question we will use the Cosine Law:
[tex]a^2=b^2+c^2-2bc\cos A.[/tex]
Substituting b=2, c=4, and A=60º in the above equation we get:
[tex]a^2=2^2+4^2-2*2*4\cos60º.[/tex]
Simplifying the above result we get:
[tex]\begin{gathered} a^2=4+16-16*\frac{1}{2} \\ =4+16-8=12. \end{gathered}[/tex]
Therefore:
[tex]a=\sqrt{12}=2\sqrt{3}.[/tex]
Answer:
[tex]a=2\sqrt{3}.[/tex]
