Question

Please help me, i dont get math at all!

Answer 1

http://tinypic.com/view.php?pic=20sc5fb&s=6

Answer 2

anyone know how to do this??

Answer 3

do you know about similar triangles? All 3 triangles, (the big one, and the 2 smaller ones) are similar.

I would use the fact that the 2 smaller ones are similar.
Set up a ratio between corresponding sides.

Answer 4

so just you need to know the thesis of the height inside a right triangle when the height bisect the rith angle exactly like in your draw

so than this thesis said that this height squared will be equal with product of two shadows of the height what the height has on hypothenuse

so in this case

DB^2 =CD*AD

DB^2 =9*12 = 108

than DB=sqrt(108)=sqrt(9*4*3)=3*2sqrt3=6sqrt3

DB=6sqrt3

hope so much that is understandably

good luck

bye

Answer 5

DB = x
x^2=9.12 (euclit http://en.wikipedia.org/wiki/Euclid)
x=3.2sqrt3
DB= 6sqrt3