SHAPES AND FIGURES OF PLANE GEOMETRY
Geometry
SHAPES AND FIGURES OF PLANE GEOMETRY
This chapter covers the calculation of the perimeter and area of selected plane
figures.
EO 1.3
STATE the definition of the following types of triangles:
a.
Equilateral
b.
Isosceles
c.
Acute
d.
Obtuse
e.
Scalene
EO 1.4
Given the formula, CALCULATE the area and the
perimeter of each of the following basic geometric
shapes:
a.
Triangle
b.
Parallelogram
c.
Circle
The terms and properties of lines, angles, and circles may be applied in the layout, design,
development, and construction of closed flat shapes. A new term, plane, must be understood in
order to accurately visualize a closed, flat shape. A plane refers to a flat surface on which lies
a straight line connecting any two points.
A plane figure is one which can be drawn on a plane surface. There are many types of plane
figures encountered in practical problems. Fundamental to most design and construction are three
flat shapes: the triangle, the rectangle, and the circle.
Triangles
A triangle is a figure formed by using straight line segments to connect three points that are not
in a straight line. The straight line segments are called sides of the triangle.
Examples of a number of types of triangles are shown in Figure 8. An equilateral triangle is
one in which all three sides and all three angles are equal. Triangle ABC in Figure 8 is an
example of an equilateral triangle. An isosceles triangle has two equal sides and two equal
angles (triangle DEF). A right triangle has one of its angles equal to 90° and is the most
important triangle for our studies (triangle GHI). An acute triangle has each of its angles less
than 90° (triangle JKL). Triangle MNP is called a scalene triangle because each side is a
different length. Triangle QRS is considered an obtuse triangle since it has one angle greater
than 90°. A triangle may have more than one of these attributes. The sum of the interior angles
in a triangle is always 180°.
MA-03
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