`cos A=cos^(2)((A)/(2))-sin^(2)((A)/(2))=1-2sin^(2)((A)/(2))=2cos^(2)((A)/(2))-1`

[cos((A)/(2))-sin((A)/(2))]^(2)=1-sin A

If : A+B+C= pi "then" : 1 - sin^(2)""(A)/(2) - sin^(2)""(B)/(2)+ sin^(2)""(C)/(2)= A) 2cos""(A)/(2) * cos sin ^(2)""(B)/(2) + sin^(2)""(C)/(2) B) 2 cos ""(B)/(2)* cos ""(B)/(2) * sin""(C)/(2) C) 2 cos ""(C)/(2)* cos ""(A)/(2) * sin""(B)/(2) D) 2 cos ""(A)/(2)* cos ""(B)/(2) * sin""(C)/(2)

Prove that: [1/(sec^(2)A-cos^(2)A)+1/("cosec"^(2)A-sin^(2)A)].sin^(2)A.cos^(2)A=(1-sin^(2)Acos^(2)A)/(2+sin^(2)Acos^(2)A)

Prove the following identities: (sin+cos A)/(sin A-cos A)+(sin-cos A)/(sin A+cos A)=(2)/(sin^(2)A-cos^(2)A)=(2)/(2sin^(2)A-1)=(2)/(1-2cos^(2)A)

Show that: sin^(8)A-cos^(8)A=(sin^(2)A-cos^(2)A)(1-2sin^(2)A cos^(2)A)

Show that: sin^(8)A-cos^(8)A=(sin^(2)A-cos^(2)A)(1-2sin^(2)A*cos^(2)A)

Prove that (1)cos2A=2cos^(2)A-1(2)cos2A=1-2sin^(2)A

Show that (i) sin^(8)A-cos^(8)A=(sin^(2)A-cos^(2)A)(1-2sin^(2)A.cos^(2)A)

Prove that: (sin A + cos A)/(sin A - cos A) + (sin A - cos A)/(sin A + cos A) = (2)/(sin^(2)A-cos^(2)A)=(2)/(2sin^(2)A-1)=(2)/(1-2 cos^(2)A) .

In a triangle ABC if (sin2A+sin2B+sin2C)/(cos A+cos B+cos C-1)=((lambda)/(2))cos((A)/(2))cos((B)/(2))cos((C)/(2)) then lambda equals