Relative to a fixed origin OOO, the vertex D D\,D of a triangular structure has position vector (4i−j+5k)(4\mathbf{i} - \mathbf{j} + 5\mathbf{k})(4i−j+5k), vertex E E\,E has position vector (5i+2j+9k)(5\mathbf{i} + 2\mathbf{j} + 9\mathbf{k})(5i+2j+9k), and vertex F F\,F has position vector (i+3j+4k)(\mathbf{i} + 3\mathbf{j} + 4\mathbf{k})(i+3j+4k).
Find the vector EF⃗\vec{EF}EF.
Show that the quadrilateral ODEF ODEF\,ODEF is a parallelogram, giving reasons for your answer.
168 exam-style questions on OCR (MEI) A Level Maths 1.11 Vectors, covering 1.11.1 Language of vectors in two dimensions, 1.11.2 Add, subtract and scale vectors, 1.11.3 Magnitude and direction of a vector, 1.11.4 Position vectors, 1.11.5 Distance between points by position vectors, 1.11.6 Vectors to solve problems, 1.11.7 Language of vectors in three dimensions (A-level only), and 1.11 Vectors. Each one has a worked solution and a mark scheme showing where the marks go.