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What sort of angles are the two others? The two others are acute angles.

What sort of angles has the obtuse-angled triangle? One obtuse and two acute angles, &c.

SECTION XIX.

Further development in regard so some essential mathematical figures.

The mother draws quadilateral figures of

four equal sides. A four-sided figure . .

which has all its sides equal, and all its

angles right angles, is called a square.''

Try whether the square I have drawn is correct. She makes three squares of equal, and two of unequal magnitude. How many equal sides has a square? how many right angles?

A four-sided figure, which i —.

has all its angles right an-
gles, but not all its sides
equal, is called an oblong, or parallelogram.

She makes two, three, four oblongs of equal, and as many of unequal size.

I will draw a four-sided figure, which has all its sides equal, but whose angles are not right, but acute and obtuse angles. Such a figure is called a rhomb. She draws a figure which has its opposite sides equal to one another, but which has not all its sides equal, nor its angles right angles. This figure is called a rhomboid. She makes three, four, five rhomboids, of equal and unequal size, which the children describe. Can you show me in any other place besides the table or slate, a square, an oblong, a rhomb, or a rhomboid?

We will draw an irregular four-sided figure: such a figure is called a trapezium.

Mother. Here is a five-sided figure, or pentagon, having all its sides equal, and five obtuse angles. Can you form such a figure, and express, by words, what you have been doing? This figure is called an equal-sided or equilateral pentagon.

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Here is a pentagon of two and of three equal sides, having two right, two equal obtuse, and one acute angle.

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Here is one having two and two sides equal and one unequal, having five acute angles.

Here is a six-sided figure, or hexagon, having all its sides equal, and therefore called an equilateral hexagon.

SECTION XX.

Drawing Exercise. Combination of Angles, Triangles, and Polygons.

Mother. Form a combination of parallel lines equally long, running in different directions. Form another of right angles, either combined or separate. Another of acute angles, of equal magnitude. A third of equal and unequal obtuse angles, &c.

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Make a combination of equilateral triangles, of equal magnitude: another of isosceles, or such triangles as have only two sides equal. A figure which is composed of right-angled triangles. Another of equal obtuse triangles, &c.

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Draw a figure by combining equilateral triangles with right angles: another by right-angled triangles with acute angles, &c.

Compose a figure of equal squares.

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Draw figures by a combination V \ of rhombs: j ^ ^

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Form different figures , .

by a combination of ~7 I \

equal lines, drawn in ^—y, difFerent directions. 2

Draw a figure by a combination of equal angles joining each other:

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