Let I be the incetre of `Delta ABC` having inradius r. Al, BI and Ci intersect incircle at D, E and F respectively. Prove that area of `DeltaDEF " is " (r^(2))/(2) (cos.(A)/(2) + cos.(B)/(2) + cos.(C)/(2))`

Let I be the incetre of ΔABC having inradius r. Al, BI and Ci intersect incircle at D, E and F respectively. Prove that area of Δ D E F is r 2 2 ( cos . A 2 + cos . B 2 + cos . C 2 ) DeltaDEF " is " (r^(2))/(2) (cos.(A)/(2) + cos.(B)/(2) + cos.(C)/(2))

Let I be the incentre of A B C having inradius rdotA I ,B Ia n dC I intersect incircle at D , Ea n dF respectively. Prove that area of D E F is (r^2)/2(cosA/2+cosB/2+cosC/2)

In DeltaABC , the bisectors of the angles A, B and C are extended to intersect the circumcircle at D,E and F respectively. Prove that AD cos.(A)/(2) + BE cos.(B)/(2) + CF cos.(C)/(2) = 2R (sin A + sin B + sin C)

Delta = 4 R r cos ""( A) /(2) cos ""( B)/(2) cos "" ( C) /(2)

Prove that : (abc)/(s) cos (A)/(2) cos (B)/(2) cos (C )/(2) = triangle .

In Delta ABC prove that cos ec(A)/(2)cos ec(B)/(2)cos ec(C)/(2)>=6

In a triangle Delta ABC , prove the following : 2 abc cos.(A)/(2) cos.(B)/(2) cos.(C )/(2) = (a+b+c)Delta

In a triangle Delta ABC , prove the following : 2 abc cos.(A)/(2) cos.(B)/(2) cos.(C )/(2) = (a+b+c)Delta

Prove that a cos^(2)(A/2)+b cos^(2)(B/2)+c cos^(2)(C/2)=s+(Delta)/(R)