[+(c-a)cot(B)/(2)+(a-)],[+cot C=(a^(2)+b^(2)+c^(2))/(4Delta)],[cot B+c^(2)cot C=4Delta]

a^(2) cot A+ b^(2) cot B+ c ^(2) cot C =

a^(2)cot A+b^(2)cot B+c^(2)cot C=

4Delta(cot A+cot B+cot C)=a^(2)+b^(2)+c^(2)

Prove that cot A + cot B + cot C = (a^(2)+b^(2)+c^(2))/(4/_\) .

( cot ""(A)/(2) + cot ""(B)/(2)+ cot ""( C )/( 2))/( cot A + cot B + cot C ) =

cot((A)/(2))+cot((B)/(2))+cot((C)/(2))=cot((A)/(2))cot((B)/(2))cot((C)/(2))

Delta ABC;(b-c)cot((A)/(2))+(c-a)cot((B)/(2))+(a-b)cot((C)/(2))

In ABC,(cot A)/(2)+(cot B)/(2)+(cot C)/(2) is equal to (Delta)/(r^(2))(b)((a+b+c)^(2))/(abc)2R(c)(Delta)/(r)(d)(Delta)/(Rr)

Delta ABC;(b-c)(cot A)/(2)+(c-a)(cot B)/(2)+(a-b)(cot C)/(2)

In a DeltaABC , 2 Delta (cot B + cot C)=