In any `DeltaABC,` prove the following : `(a+b+c)(cosA+cosB+cosC)=2((a cos^2) 1/2(A+bcos^2) 1/2(B+cos^2) 1/2C)`

Prove the following : cos2A+cos2B+cos2(A-B)+1 = 4cosA.cosB.cos(A-B)

In DeltaABC , prove that: abc. cosA/2.cosB/2.cosC/2=Deltas

In any DeltaABC , prove that a(cosC-cosB)=2(b-c)cos^(2)""1/2A

In any triangle ABC, prove that : (cosA)/a+ (cosB)/b+(cosC)/c= (a^2+b^2+c^2)/(2abc) .

In DeltaABC , prove that: a(cosC-cosB)=2(b-c)cos^(2)A/2

In DeltaABC , prove that: a(cosC-cosB)=2(b-c)cos^(2)A/2

In a triangle ABC, prove that: cos^4A+cos^4B+cos^4C= 3/2 + 2 cosA cosB cosC+ 1/2 cos 2A cos2B cos2C

In any DeltaABC , prove that (1+cos(A-B)cosC)/(1+cos(A-C)cosB)=(a^(2)+b^(2))/(a^(2)+c^(2))

cos^2 A + cos^2 B +cos^2 C=1+2cosA cosB cosC .

In any Delta A B C , prove that: (cosA)/(bcosC+c cosB)+(cosB)/(c cosA+acosC)+(cosC)/(acosB+bcosA)=(a^2+b^2+c^2)/(2a b c)