If `A+B=C,` then
`cos^(2)A+cos^(2)B+cos^(2)C-2cosAcosBcosC=`

A+B=C rArr cos^(2)A+cos^(2)B+cos^(2)C-2cos A cos B cos C=

If A+B+C=180^(@) then prove that cos^(2)A+cos^(2)B+cos^(2)C=1-2cosAcosBcosC

cos^(2)A+cos^(2)B+cos^(2)C=1-cos A cos B cos C prove that

If A+B+C= 360^(@) ,prove that: 1-cos^(2)A-cos^(2)B-cos^(2)C+2cosA cos B cos C=0

If A+B+C=180, prove that cos^(2)A+cos^(2)B+cos^(2)C=1-2cos A cos B cos C

If DeltaABC , prove that: a) sin^(2)A+sin^(2)B-sin^(2)C=2sinAsinBcosC b) cos^(2)A+cos^(2)B-cos^(2)C=1-2sinAcosBsinC c) cos^(2)A+cos^(2)B+cos^(2)C=1-2cosAcosBcosC