Respuesta :

gmany

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]

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