A = bh/2. If radius is 3 in, height is 6.
Imagine splitting the triangle into 2 pieces. It becomes a 30-60-90 triangle, with the long leg of length 6 with its angle 60 degrees. Because of its special proportions, e know if the 60D side is 6, the 30D sid is 3. which means it triangle put back together, the bottom is 6.
bh/2 = 6*6/2 = 36/2 = 18 in. squar