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

Question

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500

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Calculate

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

and enter them in that order.

Guest Apr 13, 2022

Alan · Answer 1 · 2022-04-13T07:02:37

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.

Vinculum · Answer 2 · 2022-04-13T01:21:47

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Hello, how whould I get cosb and c then?

Vinculum Apr 13, 2022

+33658

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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