SOLUTION AND PROPERTIES OF TRIANGLE | DIFFERENT CIRCLES AND CENTERS CONNECTED WITH TRIANGLE | Escribed Circle, Find the Radius of escribed circle `(i) r_1 = Delta/(s-a) = s tan (A/2) = 4 R sin (A/2) Cos (B/2 )Cos (C/2)`, Prove that `r_1+r_2+r_3-r=4R`, Prove that `cosA+cosB+cosC=1+r/R`, If in a triangle `r_1=r_2+r_3+r`; Prove that triangle is right angled., Prove that `(acosA+bcosB+c cosC)/(a+b+c)=r/R`