Bunuel wrote:
According to the figure above, does AD = BD?
(1) The degree measure of angle ABD is half that of angle BDC.
(2) The degree measure of angle DBC is 20°.
Kudos for a correct solution.damn..it's been a while since I last time solved geometry questions...
took way too long to re-check everything...
1. let's say ABD is X. BDC is 2x. Since we know that angle BDC is 2x (two times the angle ABD), we know for sure that angle ADB is 180-2x (property of the lines).
let's name BAD angle Y.
we have: 180 = x+180-2x+y
rearrange = x=y.
it means that angle ABD is equal to BAD. As such, AD is equal to BD. sufficient.
2. doesn't give much of the info alone...
A is the answer.