If `A+B+C=pi`, prove that : `cosA + cosB-cosC=4cos(A/2) cos(B/2) sin(C/2) -1`

If A+B+C=pi , prove that : sinA+sinB+sinC= 4cos( A/2 )cos( B/2) cos(C/2)

If A+B+C = pi , prove that : cosA- cosB - cosC = 1-4sinA//2cosB//2cosC//2 .

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

If A+B+C = pi , prove that : cos2A +cos2B +cos2C =-1-4cosAcosBcosC .

If A+B+C+D = 2pi , prove that : cosA +cosB+cosC+cosD=4 cos( (A+B)/2) cos((B+C)/(2) )cos( (C+A)/2)

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

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

If A,B,C are the angles of a triangle then prove that cos A+cos B-cos C=-1+4cos((A)/(2))cos((B)/(2))sin((C)/(2))

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

If A+B+C=pi/2 , prove that: sin2A + sin2B+sin2C = 4cosA cosB cosC