LESSON TWENTY-SIXTH.
KINDS OF PARALLELOGRAMS.
RHOMBOIDS.
How many quadrilaterals in the diagram? (Diagram [21].)
How many parallelograms?
Has the parallelogram a d any right angle?
It is called a “rhomboid.”
A rhomboid is a parallelogram which has no right angle.
Name five other rhomboids.
What three names may be given to Fig. 2?
Why is it a quadrilateral?
Why a parallelogram? Why a rhomboid?
RHOMBS.
Are the four sides of the rhomboid a d equal to each other?
Are the four sides of the rhomboid e h equal to each other?
If a triangle has its three sides equal to each other, what do you call it?
Then when a rhomboid has its sides equal to each other, what may it be called?
An equilateral rhomboid is called a rhombus.
A rhombus is an equilateral rhomboid.
See Note [D], Appendix.
Name two other rhombuses, or rhombs.
What four names can you give to Fig. e h?
Why a quadrilateral? Why a parallelogram? Why a rhomboid? Why a rhombus?
RECTANGLES.
Has the parallelogram i l any right angles?
How many?
It is called a “rectangle.”
A rectangle is a right-angled parallelogram.
Name four other rectangles.
What three names may be given to Fig. i l?
Why a quadrilateral? Why a parallelogram? Why a rectangle?
SQUARES.
Has the rectangle i l its four sides equal?
Has the rectangle m p its four sides equal?
It is called a “square.”
A square is an equilateral rectangle.
Name another “square.”
What four names may be given to Fig. m p?
Why a quadrilateral? Why a parallelogram? Why a rectangle? Why a square?
