19. The triangle of maximum area that can be inscribed in a given circle of radius 'r' is: (a) An isosceles triangle with base equal to 2r. (b) An equilateral triangle having each of its side of length 3r (c) A right angle triangle having two of its sides of length 2r and r. 2r (d) An equilateral triangle of height 3 ) Let F1(A,B,C) = (AB) v [C^(AVB)] VA and F (A,B)=(AvB)v (BA) be two logical expressions. Then: (a) Both F1 and F2 are not tautologies (c) F1 and F both are tautologies (b) F is not a tautology but F2 is a tautology (d) F a tautology but F is not a tautology