Answer:
38°
Step-by-step explanation:
Using the Cosine rule in Δ ABC
cos A = [tex]\frac{b^2+c^2-a^2}{2bc}[/tex]
where a, b and c are the sides of the triangle.
Here a = 5, b = 3 and c = 7 , thus
cos A = [tex]\frac{3^2+7^2-5^2}{2(3)(7)}[/tex] = [tex]\frac{9+49-25}{42}[/tex] = [tex]\frac{33}{42}[/tex] , thus
∠ A = [tex]cos^{-1}[/tex] ([tex]\frac{33}{42}[/tex] ) ≈ 38°
