I can answer this if the question concerns Penrose tiling using "kite" and "dart" tiles. The "kite" is a quadrilateral whose four corners have angles of 72, 72, 72, and 144 degrees. The "dart" is a non-convex quadrilateral whose four interior angles are 36, 72, 36, and 216 degrees.
If however if the questioner want to determine an unknown angle in of a general kite quadrilateral (two sides of length a and two sides of length b, not a parallelogram) when the length of all sides and one angle is known, then the equation [which is too complex for me to easily transcribe] can be found in the Geometry Atlas http://www.geometryatlas.com/entries/153
I can answer this if the question concerns Penrose tiling using "kite" and "dart" tiles. The "kite" is a quadrilateral whose four corners have angles of 72, 72, 72, and 144 degrees. The "dart" is a non-convex quadrilateral whose four interior angles are 36, 72, 36, and 216 degrees.
If however if the questioner want to determine an unknown angle in of a general kite quadrilateral (two sides of length a and two sides of length b, not a parallelogram) when the length of all sides and one angle is known, then the equation [which is too complex for me to easily transcribe] can be found in the Geometry Atlas http://www.geometryatlas.com/entries/153