http://img8.imageshack.us/i/snapshot20090605.jpg/
for (i) i understand 2 figures are similar if they have same
angles and length.
but i can only see common angle D, rest i cant visualize
(ii) from tangent-secant theorem,
DB^2= DC* DA
then how to continue to link to the proof?
help appreciated, thanks!
(i)
-AB bisects angle DBC, hence angle ABC = angle ABD =
45degree
-angle ADB = angle CAB
-Both triangles have DB as a common side.
= > 2 same angles, and a common side, triangle ABD and BCD
are similar triangles.
(ii)
DB^2 - DA^2 = DC*DA - DA*DA
=DA ( DC - DA )
=DA*AC
=AD*AB
Note that AC = AB.