The triangle of maximum area that can be inscribed in a given circle of radius ' $r$ ' is :\\
(1) An equilateral triangle having each of its side of length $\sqrt { 3 } r$.\\
(2) An isosceles triangle with base equal to $2 r$.\\
(3) An equilateral triangle of height $\frac { 2 r } { 3 }$.\\
(4) A right angle triangle having two of its sides of length $2 r$ and $r$.