are you familiar with the pythagorean theorem?
it's the formula
a^2 + b^2 = c^2
where 'a' and 'b' are the legs of a right triangle, c is the hypotenuse
so here,
lets take
a = unknown, b = 18, c = 36If we focus on triangle ABC, we see that AC is the hypotenuse
If we turn our attention to triangle ADB, we'll find that AB is the hypotenuse
So they are corresponding partAD is the longer leg of triangle ADB
AB is the longer leg of triangle ABC
so this is another pair of corresponding partswe then divide the corresponding parts of ABC over ADB (in the same order) like this
AC/AB = AB/AD
then plug in the info we know
36/(18sqrt(3)) = (18sqrt(3))/AD
and then solve for ADcross multiply to get
36AD = (18sqrt(3))(18sqrt(3))
36AD = 1818sqrt(3)sqrt(3)
36AD = 18^2(sqrt(3))^2
36AD = 3243
36AD = 972 AD = 972/36AD = 27hope u get it :)