If `A + B + C = 180^@,` them prove that `cos 2A + cos2B - cos2C = 1 - 4 sinA sinB sinC`

If A + B + C =180^@ , prove that : cos^2 A+ cos^2 B-cos^2 C= 1-2 sin A sin B cos C .

If A + B + C =pi , prove that : cos 2A - cos 2B- cos 2C= -1+4 cos A sinB sin C .

If A+B+C=pi , prove that : cos2A+cos2B-cos2C=1-4sinA sinB cosC

If A+B+C=180^@ , then prove that cos2A + cos2B +cos2C=-1-4cosA cosB cosC .

If A + B + C =180^@ , prove that : cos^2 A- cos^2 B-cos^2 C=2 cos A sin B sinC -1 .

If A + B + C =pi , prove that : cos 2A + cos 2B + cos 2C = -1-4 cos A cos B cos C .

If A+B+C=180^(@) then prove that the following: cos2A+cos2B-cos2C =1-4sinAsinBcosC

If A+B+C=180^0 , prove that : cos^2 A+cos^2 B-cos^2 C=1-2sinA sinB cosC

If A + B + C = 180^(@) , prove that cos A + cos B - cos C = -1 + 4 cos (A)/(2) cos"" (B)/(2) sin"" (C )/(2)

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