in triangle ABC prove that acos²A/2+bcos²B/2+ccos²C/2=s+delta/R
Answers
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Step-by-step explanation:
ANSWER
LHS =a(bcosC−ccosB)=abcosC−accosB
ANSWER
LHS =a(bcosC−ccosB)=abcosC−accosB
=ab⋅
2ab
a
2
+b
2
−c
2
−ac⋅
2ac
a
2
+c
2
−b
2
, ..... use cosine rule
=
2
1
(a
2
+b
2
−c
2
−a
2
−c
2
+b
2
)=b
2
−c
2
=R.H.S.
Hence proved.
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