Answer:
[tex]DC=\frac{8}{3}\ units[/tex]
Step-by-step explanation:
The picture of the question in the attached figure
we know that
The triangle ABD is an isosceles triangle
because
AB=BD
The segment BM is a perpendicular bisector segment AD
so
In the right triangle ABM
Applying the Pythagorean Theorem
[tex]BM^2=AB^2-AM^2[/tex]
we have
[tex]AB=5\ units\\AM=x\ units[/tex]
substitute
[tex]BM^2=5^2-x^2[/tex]
[tex]BM^2=25-x^2[/tex] -----> equation A
In the right triangle BMC
Applying the Pythagorean Theorem
[tex]BM^2=BC^2-MC^2[/tex]
we have
[tex]BC=7\ units\\MC=AC-AM=(9-x)\ units[/tex]
substitute
[tex]BM^2=7^2-(9-x)^2[/tex]
[tex]BM^2=49-(81-18x+x^2)[/tex]
[tex]BM^2=49-81+18x-x^2[/tex]
[tex]BM^2=-x^2+18x-32[/tex] ----> equation B
equate equation A and equation B
[tex]-x^2+18x-32=25-x^2[/tex]
solve for x
[tex]18x=25+32\\18x=57\\\\x=\frac{57}{18}[/tex]
Simplify
[tex]x=\frac{19}{6}[/tex]
Find the length of DC
[tex]DC=AC-2x[/tex]
substitute the given values
[tex]DC=9-2(\frac{19}{6})[/tex]
[tex]DC=9-\frac{19}{3}\\\\DC=\frac{8}{3}\ units[/tex]
