Question

Find the measure of angle A if a = 34, b = 28 and c = 15

Answer 1

I have this but I dont know what should I do next.
34^2= 28^2+15^2 -2(28*15) COS A

6.84 = Cos A

Answer 2

cosine A = (-a² + b² + c²)/ABC A = arccos((-a² + b² + c²)/abc) = arccos(-34² + 28² + 15²)/14280 = arccos(-147/14280) = 90.59° :)

Answer 3

thank you !

Answer 4

your very welcome ! :)