Explanation: To mark point D accurately on the graph, we need to use the X tool as instructed. First, locate point A on the graph. Then, draw a straight line from point A to point B. Next, draw another straight line from point B to point C.

An arrowhead is a quadrilateral with two pairs of adjacent sides equal in length, and one of whose interior angles is a reflex angle. The diagonal through this angle is a line of symmetry for the shape.

The arrowhead has a few special properties. The main property that makes it different to other quadrilaterals is that the diagonals bisect externally to the polygon and are perpendicular to one another. Similar to a kite, the arrowhead has two pairs of adjacent sides that are equal length.

Concave quadrilaterals. In a concave quadrilateral, one interior angle is bigger than 180°, and one of the two diagonals lies outside the quadrilateral. A dart (or arrowhead) is a concave quadrilateral with bilateral symmetry like a kite, but where one interior angle is reflex.

Problem. Student Solutions. ABCD is a non-convex quadrilateral. The points P, Q, R and S are the midpoints of the edges of ABCD. You can change the shape of the quadrilateral ABCD.