Half Angle Formula of `sin (A/2) ,Sin (B/2) ,sin(C/2)`

If A, B, C are angle of a triangle ABC, then the value of the determinant |(sin (A/2), sin (B/2), sin (C/2)), (sin(A+B+C), sin(B/2), cos(A/2)), (cos((A+B+C)/2), tan(A+B+C), sin (C/2))| is less than or equal to

If A,B,C and D are angles of quadrilateral and sin(A)/(2)sin(B)/(2)sin(C)/(2)sin(D)/(2)=(1)/(4) , prove that A=B=C=D= pi//2

If A+B+C = 180^0 , Prove that : sin^2 (A/2) + sin^2 (B/2) + sin^2 (C/2) =1-2 sin (A/2) sin (B/2) sin (C/2)

If A+B+C=pi , prove that : (sin 2A+sin 2B + sin 2C)/(sinA+sinB+sinC) = 8 sin(A/2) sin(B/2) sin(C/2)

If A+B+C=pi , Prove that : sin( A/2) + sin( B/2) + sin(C/2) =1 + 4 sin( (B+C)/(4)) sin( (C+A)/(4)) sin( (A+B)/(4))

(sin2A + sin2B + sin2C) / (sin A + sin B + sin C) = 8sin ((A) / (2)) sin ((B) / (2)) sin ((C) / (2))