`cos(A/2)+cos(B/2)-cos(C/2)=4cos((pi+A)/4)cos((pi+B)/4)cos((pi-c)/4)`

In triangle ABC,prove that cos((A)/(2))+cos((B)/(2))+cos((C)/(2))=4(cos(pi-A))/(4)(cos(pi-B))/(4)(cos(pi-C))/(4)

If A+B+C=pi , prove that : sin ((B+C)/(2)) + sin ((C+A)/(2)) + sin( (A+B)/(2) )= 4cos ((pi-A)/(4)) cos( (pi-B)/(4)) cos((pi-C)/(4)) .

If A+B-C=3pi, t h e n sin A+ sin B-sin C is equal to- a.4sin(A/2)sin(B/2)cos(C/2) b. -4sin(A/2)sin(B/2)cos(C/2) c. 4cos(A/2)cos(B/2)cos(C/2) d. -4cos(A/2)cos(B/2)cos(C/2)

If A+B+C=pi then prove cos( (A)/2) cos( (B-C)/2) + cos( B/2) cos((C-A)/2) + cos( C/2) cos( (A-B)/2) = sinA +sinB+sinC

cos((pi)/(15))cos((2 pi)/(15))cos((pi)/(5))cos((4 pi)/(15))cos((2 pi)/(5))cos((7 pi)/(15)) is equal to

In triangle ABC, prove that sin((A)/(2))+sin((B)/(2))+sin((C)/(2))<=(3)/(2) Hence,deduce that cos((pi+A)/(4))cos((pi+B)/(4))cos((pi+C)/(4))<=(1)/(8)

Prove that 4cos((2pi)/7).cos(pi/7)-1=2cos((2pi)/7) .

The value of cos((pi)/(7))+cos((2 pi)/(7))+cos((3 pi)/(7))+cos((4 pi)/(7))+cos((5 pi)/(7))+cos((6 pi)/(7))+cos((7 pi)/(7)) is 1(b)-1(c)0(d) none of these

cos A+cos((4 pi)/(3)-A)+cos((4 pi)/(3)+A)=0

The value of cos[(1)/(2)cos^(-1)cos((14 pi)/(5))]is(a)cos((2 pi)/(5))(b)cos(-(7 pi)/(5))(c)sin((pi)/(10))(d)-cos((3 pi)/(5))