Hello helloying:

Draw a horizontal line through point E.

This forms some right triangles with leg measures of 10 and 17 because point E is vertically and horizontally centered inside the rectangle.

Therefore, the measure of half of angle BEC can be found using the inverse tangent function with the ratio 10/17.

Double the result.

Actually, you do not need the horizontal line because half of angle BEC is the same as the measure of angle BAE. And the ratio 20/34 simplifies to 10/17, which brings us back to the same input for the inverse tangent function.

Cheers,

~ Mark