Question

multiple similarity transformations are performed on a triangle. which elements must be preserved?
orientation
side length
angle measure
overall size

Explanation:

Similarity transformations (such as dilation, rotation, translation, reflection) change orientation (in case of reflection), side - length (in case of dilation), and overall size (in case of dilation). But by the definition of similar triangles, the ratio of side - lengths is constant and the angle measures are equal. So angle measure is preserved.

Answer:

angle measure