If `r/(r_1)=(r_2)/(r_3),` then `A=90^0` (b) `B=90^0` `C=90^0` (d) none of these

If an a triangle A B C ,(2cosA)/a+(cosB)/b+(2cosC)/c=a/(b c)+b/(a c), find the /_A= 90^0 (b) 60^0 (c) 30^0 (d) none of these

If (r)/(r _(1))= (r_(2))/(r _(3)), then show that c=90^(@).

If A B , B C a n d C D are equal chords of a circle with O as centre and A D diameter, then /_A O B= 60^0 (b) 90^0 (c) 120^0 (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 (1+x+x^2+x^3)^n=sum_(r=0)^300 b_rx^r and k=sum _(r=0)^300 b_r=k, then sum_(r=0)^300 r. b_r, is (A) 50.4^100 (B) 150.4^100 (C) 300.4^100 (D) none of these

If sum_(r=0)^(n)(r)/(nC_(r))=sum_(r=0)^(n)(n^(2)-3n+3)/(2*^(n)C_(r)), then n=1 b.n=2c.n=3d .none of these

(1+x)^(n)=sum_(r=0)^(n)a_(r)x^(r)&b_(r)=1+(a_(r))/(a_(r-1))&prod_(r=1)^(n)b_(r)=((101)^(100))/(100!) then equals to: 99(b)100(c)101(d) None of these

In any triangle,the minimum value of r_(1)r_(2)r_(3)/r^(3) is equal to 1(b)9(c)27(d) none of these