Radius of circumcircle of `/_\DEF` is
`(A) R`
`(B)` `R/2`
`(C)` `R/4`
`(D)` none of these

In A B C ,(a b-r_1r_2)/(r_3),w h e r ea ,b ,r_1r_2, r_3, Ra n dr have usual meanings, is equal to (A) R (B) 2R (C) r (D) none of these

In an equilateral triangle, the inradius and the circumradius are connected by r=4R b. r=R//2 c. r=R//3 d. none of these

If a=sum_(r=1)^oo(1/r)^2, b=sum_(r=1)^oo1/((2r-1)^2), then a/b= (A) 5/4 (B) 4/5 (C) 3/4 (D) none of these

If C_r stands for .^nC_r and sum_(r=1)^n (r.C_r)/(C_(r-1)) =210 then n= (A) 19 (B) 20 (C) 21 (D) none of these

In any triangle, the minimum value of r_1r_2r_3//r^3 is equal to (a) 1 (b) 9 (c) 27 (d) none of these

If R is the largest equivalence relation on a set A and S is any relation on A , then (a) RsubS (b) SsubR (c) R=S (d) none of these

If the sum of the areas of two circles with radii r_1 and r_2 is equal to the area of a circle of radius r , then r_1^2 +r_2^2 (a) > r^2 (b) =r^2 (c)

The values of x for which the matrix [[x+a,b,c],[a,x+b,c],[a,b,x+c]] is non-singular are (A) R-{0} (B) R-{-(a+b+c)} (C) R-{0,-(a+b+c)} (D) none of these

If sum _(r=1)^n (r^2+1)r! =200xx201! Then n= (A) 200 (B) 201 (C) 199 (D) none of these

The range of the function f(x)=(x^2-x)/(x^2+2x) is R (b) R-[1] (c) R={-1/2,1} (d) none of these