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Measure and draw with modern measuring instruments
Measure the lengths in mm of the indicated line sections in the following sketch.
Which measuring-instrument is the most suitable?
Hint for the Teacher:
Allow a margin of ± 2 mm to both sides, but encourage learners to measure accurately all the same.
Background:
What is a line section?
The line sections used to compile the sketch above are mainly HORIZONTAL, VERTICAL, DIAGONAL (slanting) or CURVED.
What is a horizontal line?
What is a vertical line?
What is a diagonal line?
What is a curved line?
How?
Using a ruler and the four kinds of lines, design and draw any object on squared paper.
a. Draw a horizontal line of 50 mm with your ruler. Follow the instructions
b) Draw a diagonal line of 70 mm with your ruler. Follow the instructions given above.
Draw a line parallel to each of the following:
Background:
Complete: The point where two lines meet, is called a .The size of an angle is measured in DEGREES and we use a PROTRACTOR to measure the size of an angle.
When a vertical line meets a horizontal line perpendicularly, a __ is formed. The size of such an angle is 90 ^{o} .
A line section can also be called a STRAIGHT ANGLE. The size of such an angle is 180 ^{o} .
When an angle is between 0 ^{o} and 90 ^{o} , it is called an ACUTE ANGLE and when an angle is between 90 ^{o} and 180 ^{o} , it is called an OBTUSE ANGLE.
Write down what kind of angle each of the following is:
Hint:
Turn the page so that one side of the angle is horizontal, and decide then.
a. A right angle
b. An acute angle
c. An obtuse angle
Background:
If we combine certain line sections with the above-mentioned three angles, we get GEOMETRICAL FIGURES. They are also called two-dimensional shapes, because they are flat shapes or planes. Lines that are one-dimensional are used in drawings to form two-dimensional shapes or planes. Most two-dimensional figures have two dimensions, namely length and breadth.
Can you recognise these basic geometrical figures?
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