Finding an angle when three sides are given

King E

New member
Joined
Nov 24, 2021
Messages
1
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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Steven G

Elite Member
Joined
Dec 30, 2014
Messages
12,215
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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