Remember that to find the area of a parallelogram, you need the height,
which is the perpendicular distance from the base to the opposite side. You
can use a side of a parallelogram for the height only when the side is
perpendicular to the base, in which case you have a rectangle.
FIVE SPECIAL QUADRILATERAL TYPES
Rectangles: A rectangle is a four-sided figure with four right angles. Opposite
sides are equal. Diagonals are equal. The perimeter of a rectangle is equal to
the sum of the lengths of the four sides, which is equal to 2(length + width).
Area of Rectangle = length × width
1. Trapezoid: Exactly one pair of parallel sides.
Parallelogram: Two pairs of parallel sides.
Area of Parallelogram = base × height
2.
Rectangle: Four right angles Perimeter of Rectangle = 2(length +
width) Area of Rectangle = length × width
3.
Rhombus: Four equal sides Perimeter of Rhombus = 4 × side Area
of Rhombus = base × height
4.
Square: Four right angles and four equal sides Perimeter of
Square = 4 × side Area of Square = (side)^2