What i tried
Drawing a line from A to E, calling it line AE, we can see 2 triangles that are simillar, triangle AEC and triangle FED. And due to this property of simillar triangles, this imply that Length ED is the same length as CE, thus length ED is also 20.9cm. Since length EP is half that of length EF, length EP is 3cm. Length DP is then 4cm due to Pythagoras theorem. Thus with length ED, EP and DP known, we cam find angle P through the Cosine rule.
Am i correct could anyone please explain. Thanks