Prove that,
`tan((A)/(2)+B)=(c+b)/(c-b)tan((A)/(2))`

In triangle ABC, prove that, tan((B-C)/(2))=(b-c)/(b+c)cot((A)/(2)) tan((C-A)/(2))=(c-a)/(c+a)cot((B)/(2)) tan((A-B)/(2))=(a-b)/(a+b)cot((C)/(2))

For any triangle ABC, prove that : sin""(B-C)/(2)=(b-c)/(a)cos((A)/(2))

For any triangle ABC, prove that : (a-b)/(c )=(sin((A-B)/(2)))/(cos((C)/(2)))

For DeltaABC , prove that, (a+b)/(c)=(cos((A-B)/(2)))/(sin""(C)/(2)) .

For any triangle ABC, prove that : (a+b)/(c)=(cos((A-B)/(2)))/(sin""(C)/(2))

If a^(2) + 2bc, b^(2) + 2ac, c^(2) + 2ab are in A.P then prove that (1)/(b-c), (1)/(c-a) and (1)/(a-b) are in A.P.

By using above basic addition/ subtraction formulae, prove that (i) tan (A+B)=(tan A+tan B)/(1-tan A tan B) , (ii) tan (A-B)=(tan A-tanB)/(1+tan A tan B) (iii) sin2theta=2sintheta costheta , (iv) cos2theta=cos^(2)theta=1-2sin^(2)theta=2cos^(2)theta-1 (v) tan 2theta=(2 tan theta)/(1-tan^(2) theta)

For DeltaABC , prove that, (cosA)/(a)+(cosB)/(b)+(cosC)/(c)=(a^(2)+b^(2)+c^(2))/(2abc) .

For any triangle ABC, prove that : (cosA)/(a)+(cosB)/(b)+(cosC)/(c)=(a^(2)+b^(2)+c^(2))/(2abc)

If a,b,c are in HP, then prove that sin ^(2) ""(A)/(2), sin ^(2) ""(B)/(2), sin ^(2) ""(C )/(2) are also in HP.