Quadrilateral-Basic Notions
Quadrilateral - Definition
Given four distinct points A, B, C and D of the same plane, neither three points are collinear ones. If segments AB, BC, CD and AD intersect only at the ends, the joining of these segments is a quadrilateral. A quadrilateral is also called a four-sided polygon, with four angles.
Analysis
Move points A, B, C or D. Will these four points always determine a quadrilateral?
ELEMENTS OF THE QUADRILATERALS
CONVEX QUADRILATERAL AND CONCAVE QUADRILATERAL
Analysis
Check the "Show / Hide internal angles" box. Move the vertices and observe what happens with the angles and the quadrilateral. Write another definition for convex and concave quadrilaterals.
SUM OF THE INTERNAL ANGLES OF QUADRILATERALS
Analysis
Check the option "Show / Hide diagonal" and demonstrate why the sum is always 360º.
Analysis
Check the "Show / Hide diagonal" option and explain why the sum is always equal to 360º.