The diagonals of a rhombus divide the figure into four congruent right triangles. Angle DAB is bisected by EA, so angle EAB is 46°/2 = 23°. EB is the side opposite, so the relevant trig relation is ...
Sin = Opposite/Hypotenuse
sin(EAB) = EB/AB
EB = (4 in)sin(23°) . . . . . . multiply by the hypotenuse
