Find the midpoint of BD.

(a/2, a/2)

Step-by-step explanation:

Coordinates of B & D are; (0, a) and (a, 0) respectively.

The formula for calculating coordinates of midpoint is;

M = ((x1 + x2)/2), ((y1 + y2)/2)

Coordinates of BD will be;

M_BD = ((0 + a)/2), ((a + 0)/2)

M_BD = (a/2, a/2)

0.02

step-by-step explanation:

time of 9 192 631 770 periods of the radiation corresponding to the transition between the 2 hyperfine levels of the ground state of the caesium 133 atom at 0 k (but other seconds are sometimes used in astronomy)