In the figure, AB = BC = CD = DE = EF = FG = GA. Then DAE is approximately:
                              

The length of the common chord of two circles of radii 15 cm and 20 cm, whose centres are 25 cm apart, is (in cm):

ABCDEFGH is a regular octagon. A and E are opposite vertices of the octagon. A frog starts jumping from vertex to vertex, beginning from A. From any vertex of the octagon except E, it may jump to either of the two adjacent vertices. When it reaches E, the frog stops and stays there. Let a_n be the number of distinct paths of exactly n jumps ending in E. Then, what is the value of a_2n-1?