Answer:
A
Step-by-step explanation:
using the Cosine Rule in Δ ABC
cosA = [tex]\frac{b^2+c^2-a^2}{2bc}[/tex]
where a, b, c are the sides opposite A, B , C
here a = 10 , b = 12 , c = 8
cosA = [tex]\frac{12^2+8^2-10^2}{2(12)(8)}[/tex] = [tex]\frac{144+64-100}{192}[/tex] = [tex]\frac{108}{192}[/tex] , then
∠ A = [tex]cos^{-1}[/tex] ( [tex]\frac{108}{192}[/tex] ) ≈ 55.8° ( to the nearest tenth )
