If `A+B+C=pi`then prove that`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)=4cos(pi-A)/4cos(pi-B)/4cos(pi-C)/4

Prove that cos(2pi)/(15)cos(4pi)/(15)cos(8pi)/(15)cos(14pi)/(15)=1/(16)

"cos(pi/15)cos((2pi)/15)cos((4pi)/15)cos((8pi)/15)=k

If A+B+C=180 , prove that: sinA+sinB+sinC=4cos(A/2)cos(B/2)cos(C/2)

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

Prove that cos((2pi)/(15))cos((4pi)/(15))cos((8pi)/(15))cos((14pi)/(15))=1/(16)

Prove that cos((2pi)/(15))cos((4pi)/(15))cos((8pi)/(15))cos((16pi)/(15))=1/(16)

Prove that: cos(pi/5)cos((2pi)/5)cos((4pi)/5)cos((8pi)/5)=(-1)/16

Prove that cos ""(pi)/(9) cos ""( 2pi)/(9) cos "" (3pi)/(9) cos ""(4pi)/(9) = (1)/(2 ^(4)).

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