Answer:
a = 8.1
Step-by-step explanation:
Use the cosine rule:
[tex]a = \sqrt{b^2 + c^2 -2 bc \space\ cosA }[/tex]
Substituting the values:
[tex]a = \sqrt{10^2 + 12^2 -2(10)(12) \space\ cos 42 \textdegree\ }[/tex]
⇒ [tex]a = \sqrt{4 \space\ cos 42\textdegree\ }[/tex]
⇒ [tex]a = 8.1[/tex]
