$$? = \angle CDB = x$$swerve wrote:
In the triangle above what is the measure of angle CDB?
1. Angle CAB = angle ACB = 30°.
2. AB = BC = BD.
Source: e-GMAT
(All angles are measured in degrees.)
(1) Using the exterior angle property (to justify 30+30 in red), triangle BCD is equilateral (hence x=60). Sufficient!
(2) The constructions shown below are viable and present two different possible values for x. Insufficient!
This solution follows the notations and rationale taught in the GMATH method.
Regards,
Fabio.
