Answer: AE = 5
Explanation:
I sketched the triangle based on the information provided.
since ∠A = 90° and is divided into three equal angles, then ∠BAD, ∠DAE, and ∠CAE = 30°
Since AB = 5 and BC = 10, then ΔCAB is a 30°-60°-90° triangle which implies that ∠B = 60° and ∠C = 30°
Using the Triangle Sum Theorem, we can conclude that ∠ADB = 90°, ∠ADE = 90°, ∠ AED = 60°, AND ∠ AEC = 120°
We can see that ΔAEC is an isosceles triangle. Draw a perpendicular to divide it into two congruent right triangles. Label the intersection as Z. ΔAEZ and ΔCEZ are 30°-60°-90° triangles.
Using the 30°-60°-90° rules for ΔABC we can calculate that AC = 5√3.
Since we divided ΔAEC into two congruent triangles, then AZ =

Now use the 30°-60°-90° rules to calculate AE = 5