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In triangle ABC, we have ab=5, bc= 8 and ac=7, as shown below:


Calculate

 

\(\cos (\angle A), \cos (\angle B), \cos (\angle C)\)

 

and enter them in that order.

 Apr 13, 2022
 #3
avatar+33151 
+1

Use the Cosine rule: \(\cos A = \frac{b^2+c^2-a^2}{2bc}\)

 

Here:  a = 8, b = 7, c = 5

 

Cycle a, b and c for the other angles.

 Apr 13, 2022
 #4
avatar+578 
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Hello, how whould I get cosb and c then?

 Apr 13, 2022
 #5
avatar+33151 
0

For cos B change the formula so that A → B, a → b, b → c, c → a

 

See if you can then work out what to do for cos C.

Alan  Apr 13, 2022

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