Answer:
21.40 ft
Explanation:
Angle BD is bisecting of ∠B, so we have to find ∠ B first. We have opposite(AC) and adjacent(BC) length, to find ∠B we can use tan formula.
tan ∠B= AC/BC
∠B= arctan(60ft/40ft)
∠B= 56.31 °
The ∠CBD bisect ∠B, so it equal to half of the angle. Angle CBD will be:
∠CBD= ∠B/2= 56.31 /2
∠CBD= 28.15 °
We have the angle(CBD) and adjacent(BC) length, now we can find DC using tan formula.
tan ∠CBD= DC/BC
DC= tan 28.15° * 40ft
DC= 0.53507226 * 40ft
DC= 21.40 ft