Answer:
Step-by-step explanation:
You end up with a 30°-60°-90° triangle inside of △ABC.
The sides of a 30°-60°-90° triangle are always in the ratio 1:√3:2.
AB is opposite the 30° angle. AM is opposite the 90° angle and has length 10, so AB is half the length of AM.
AB = 5 units.
