Then a+b=3P, let the volume that can rotate around side A be v = π b 2 * a = 3p π b 2-π b 3, and let v' = 6 π b-3 π b 2 > when 0, b∈(0, 2P), v has a single increase and a maximum value.
Therefore, when b=2P and a=P, the volume of the rotator is the largest.
Because the rectangle is a special parallelogram, the extended data contains the attributes of parallelogram. The properties of rectangles can be roughly summarized as follows:
(1) rectangle has all the properties of parallelogram: the opposite sides are parallel and equal, the diagonal lines are equal, the adjacent angles are complementary, and the diagonal lines are equally divided;
(2) All four corners of a rectangle are right angles;
(3) The diagonals of the rectangles are equal;
(4) Unstable (easily deformed).
decision
Common methods for judging rectangles are as follows:
(1) A parallelogram with right angles is a rectangle;
(2) Parallelograms with equal diagonals are rectangles.
(3) A quadrilateral with three right angles is a rectangle.
(4) Theorem: It has been proved that in the same plane, any two angles are right angles, and any group of quadrangles with equal opposite sides are rectangles.
(5) Quadrilaterals with equal diagonals and bisecting each other are rectangles.