Answer:
m∡ A = 53°
Step-by-step explanation:
Use cosine law (look at the picture).
We have:
[tex]a=13,\ b=14,\ c=15[/tex]
Substitute:
[tex]13^2=14^2+15^2-2(14)(15)\cos A\\\\169=196+225-420\cos A[/tex]
[tex]169=421-420\cos A[/tex] subtract 421 from both sides
[tex]-252=-420\cos A[/tex] divide both sides by (-420)
[tex]\dfrac{-252}{-420}=\cos A\to \cos A=0.6\\\\m\angle A\approx53^o[/tex]
