Hi melguy,

The word "bisect" means "to cut into 2 equal pieces"; for example, bisecting a 20 degree angle would yield two 10 degree angles. Knowing that definition will make this DS question fairly straightforward.

GMAT assassins aren't born, they're made,
Rich

If anyone wishes to attempt the original question, here's one solution:

Target question: What is the measure of angle BAD?

Statement 1: AD bisects angle BAC
Since we don't know the measure of angle BAC, there's no way to determine the measure of angle BAD
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: BAC is an isosceles right triangle
This statement contains no information about D, so there's no way to determine the measure of angle BAD
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
If BAC is an isosceles right triangle, then angle BAC = 45 degrees
If AD bisects angle BAC, then angle BAD = 22.5 degrees
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer = C

Cheers,
Brent