Angle bisector theorem:
CD/DB=AC/AB
REeplacing the known values:
CD/4=5.6/5.1
Solving for CD. Multiplying both sides of the equation by 4:
4(CD/4)=4(5.6/5.1)
CD=22.4/5.1
CD=4.392156863
Rounded to one decimal place:
CD=4.4
Answer: The length of CD is 4.4