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.
Main Theorems. The diagonals of a quadrilateral can determine whether it is a parallelogram, a rectangle, a rhombus, etc.. We will list and prove the main theorems here. Theorem 1: If the diagonals of a quadrilateral bisect each other then the quadrilateral is a parallelogram.Proof: Let the quadrilateral be ABCD with diagonals AC and BD intersecting at P : Then AP = PC and DP = PB since the diagonals bisect each other.Now consider triangles APD and CPB.heorem 6: If the diagonals of a parallelogram are perpendicular, then the parallelogram is a rhombus. Proof: Let the parallelogram be ABCD with perpendicular diagonals AC and BD intersecting at P : The diagonals of a parallelogram bisect each other, so triangles APB and CPB are congruent by SAS.