Finding an angle when three sides are given

King E

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Nov 24, 2021
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Consider a ΔABC.

The three sides given are:

AB = 8cm

AC = 15cm

BC = 17cm

The angle required is ∠A.

If I apply Pythagoras theorem, that is BC² = AB² + AC² in this case, then I come to know that it is a right angle.



Is there a way to find ∠A without using the Pythagoras theorem BC² = AB² + AC² ?
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You can also use Heron's formula to find the area and hence the length AD. Then you can find the two angles which make up <A.
 
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