Medium tangrams drop the internal outlines: you get the plain silhouette and have to work out the dissection yourself. There are usually several ways to fit the pieces, but expect a rotated piece or two and at least one spot where the obvious placement is wrong.
The reliable approach is corners first: every sharp point in the silhouette can only be made by a triangle tip, which pins down more than you would think. If a board stalls, the how-to-play guide covers the core techniques, and the Hint button will place one piece for you.