Suppose that in Fig.2,the length of side of square ABCD is 1,E and F are mid-points of CD and AD respectively,GE and CF intersect at a point P.Then the length of line segment CP is
Let a be the length of a diagonal of a square,b and c be the length of two diagonals of a rhombus respectively.If b:a=a:c,then the ratio of area of the square and rhombus is( ) (英汉词典:length长度;diagonal对角线;square正方形;rhombus菱形;respectively分别地;ratio比;area面积)