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Part II – Geometry – plane figures, solid figures, angles, shapes
I. Identifying plane figures (polygons), solid figures, angles
Label the pictures with the given expressions.
a circle
a square
a triangle
a cone
a rectangle
a cube
an acute angle
(an angle less than 90 degrees)
a hexagon
a sphere
a right angle
an ellipse
a cylinder
an obtuse angle
(an angle between 90 and 180 degrees)
II. Describing shapes.
SHAPE / SOLID
FIGURE
a circle
a triangle
a cone
a rectangle
a sphere
an ellipse
a cylinder
a square
a cube
© Marija Šubic, prof.
DESCRIPTION
A DVD is …
One side of a pyramid is …
A traffic cone is …
A picture is …
A marble is …
A SLO sticker is …
A CocaCola tin is…
A traffic sign is …
A dice is …
Part II
III. Triangles
1. What is a triangle?
A triangle is a 3-sided polygon (plane figure).
2. Types of triangles
Triangles can be classified according to the length of their sides and the size of their angles.
Interactive exercise
http://www2.arnes.si/~sspmsubi/triangles.htm
3. Perimeter of a triangle
The perimeter of a triangle is the sum of the lengths of its sides.
If the three sides are labelled a, b, and c, the perimeter P can be found by the following
formula: P = a + b + c
Example:
Find the perimeter of a triangular garden with sides measuring 5 meters, 9 meters and 11 meters.
Solution: …………………………………………….
4. Area of a triangle
The area of a triangle is the space bounded (enclosed) by its sides.
The sides can be of any lengths and at any angles to each other. All you have to know in order
to find the area of a triangle is the length of its base and its perpendicular height.
In this triangle, the three sides are a, b and c.
h is the perpendicular height and b is the base of the triangle. For any
triangles, if you know the base (b) and the height (h), you can always
find its area.
Formula for area of triangle
Calculating the area of a triangle - the best known and simplest formula is:
Example:
A triangular-shaped yard has a base of 25 meters and a height of 12 meters. What is its area?
Solution: …………………………………………….
IV. HOMEWORK
Do the interactive exercise on the class blog.
http://www2.arnes.si/~sspmsubi/shapes555.htm
© Marija Šubic, prof.
Part II