JEE Advanced Model Paper 8 with solutions for online practice

We know that R = abc/4Δ , so that Δ1,Δ2 and Δ3 sent the areas of Δs OBC, OCA and OABrespectively. We know OA = OB = OC = R. Then R1 = a . R . R/4 Δ1 or a/R1 = 4Δ1∕R2 . Similarly,
b/R2 = 4Δ2∕R2 , c/R3 = 4Δ2∕R2
aR1−1 + 2R2−1 + cR3−1 = 4R−2 (Δ1+Δ2+Δ3) = 4R−2Δ = 4R−2 (abc/4R) = abc/R3