Answer:
4.99 units
Step-by-step explanation:
Considering ∆ABD in the figure given, <ABD = <ABC = 90° (angle on a straight line)
Therefore, we would consider ∆ABD as a right angled triangle having side AB = 3 units, and angle D = 31°
==>Use trigonometric function to solve for the length of side BD
Side BD is the adjacent side to the angle given, while side AB is the opposite side to the angle given.
Thus,
tan D = opposite/adjacent
tan 31 = 3/BD
0.6009 = 3/BD
multiply both sides by BD
0.6009*BD = 3
Divide both sides by 0.6009 to make BD the subject of formula
BD = 3/0.6009
BD ≈ 4.99 units
