The avian cardiovascular system is able to quickly respond to changes in levels of activity (e.g., resting vs. flying) via changes in heart rate, cardiac output, & blood flow (by vasocontriction and vasodilation of vessels).
A square is a quadrilateral with all right angles and all equal sides. A square is also a parallelogram, a rectangle, and a rhombus and has all the properties of all these special quadrilaterals. Figure 3 shows a square. Figure 3 A square has four right angles and four equal sides. Figure 4 summarizes the relationships of these quadrilaterals to one another.
Parallelograms that are not also rectangles cannot be inscribed in a circle: they are not cyclic quadrilaterals. A circle that passes through three of the vertices is either too large to pass through the fourth (blue circle at the left) or too small to pass through the fourth (red circle at the right).