To answer this problem, let us first discuss what is a similar triangle:
Similar triangle is defined as having two or more triangles that have all corresponding angles that are equal and all corresponding sides that are proportionate. It does not matter what direction the triangles are facing. Their size does not matter as long as each side is proportionate.
In figure shown, it is observed that the the corresponding angles are equal and sides are proportionate. Thus,Triangle ABC and triangle DEC are SIMILAR.