constructing special angles without a protractor building special angles without a protractor

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You are watching: How to find the degree of an angle without a protractor

In this chapter, you will certainly learn exactly how to construct, or draw, various lines, angles and shapes. You will certainly use illustration instruments, such together a ruler, to draw straight lines, a protractor come measure and also draw angles, and also a compass to draw arcs that are a specific distance from a point. V the assorted constructions, you will investigate few of the nature of triangles and quadrilaterals; in various other words, you will discover out an ext about what is always true around all or certain varieties of triangles and also quadrilaterals.

## Bisecting lines

When us construct, or draw, geometric figures, we regularly need to bisect present or angles.Bisect method to reduced something right into two same parts. Over there are various ways to bisect a heat segment.

### Bisecting a heat segment with a ruler

review through the complying with steps.

Step 1: attract line segment abdominal muscle and recognize its midpoint.

Step 2: Draw any line segment v the midpoint.

The little marks on AF and also FB show that AF and FB space equal.

CD is referred to as a bisector because it bisects AB. AF = FB.

usage a leader to draw and also bisect the following line segments: ab = 6 cm and also XY = 7 cm.

In great 6, friend learnt just how to usage a compass to draw circles, and also parts of circles called arcs. We deserve to use arcs come bisect a line segment.

### Bisecting a heat segment with a compass and also ruler

review through the following steps.

Step 1

ar the compass ~ above one endpoint that the line segment (point A). Attract an arc above and below the line. (Notice the all the clues on the arc aboveand below the line are the same distance from suggest A.)

Step 2

Without changing the compass width, ar the compass on point B. Draw an arc over and listed below the line so that the arcs cross the first two. (The 2 points wherein the arcs cross are the very same distance away from allude A and also from point B.)

Step 3

use a leader to sign up with the points whereby the arcs intersect.This line segment (CD) is the bisector of AB.

Intersect means to overcome or meet.

A perpendicular is a line the meets an additional line at an edge of 90°.

Notice that CD is likewise perpendicular come AB. So it is also called a perpendicular bisector.

job-related in your exercise book. Usage a compass and also a ruler to practise illustration perpendicular bisectors on line segments.

Try this!

Work in your exercise book. Use only a protractor and ruler to attract a perpendicular bisector on a heat segment. (Remember the we usage a protractor to measure angles.)

## Constructing perpendicular lines

### A perpendicular line from a provided point

Step 1

Place her compass on the given suggest (point P). Attract an arc throughout the line on each side that the offered point. Perform not adjust the compass broad when drawing the 2nd arc.

Step 2

From every arc on the line, draw another arc ~ above the opposite next of the heat from the given suggest (P). The two new arcs will intersect.

Step 3

Use your leader to join the given suggest (P) come the suggest where the arcs crossing (Q).

PQ is perpendicular to AB. We also write it like this: PQ âŠ¥ AB.

use your compass and also ruler to attract a perpendicular heat from each given point to the line segment:

### A perpendicular heat at a given point on a line

review through the following steps.

Step 1

Place your compass on the given point (P). Attract an arc across the line on every side the the provided point. Carry out not change the compass width when drawing the second arc.

Step 2

Open her compass so the it is wider than the distance from one of the arcs come the point P. Place the compass on each arc and also draw an arc above or below the suggest P. The two brand-new arcs will intersect.

Step 3

Use your ruler to join the given suggest (P) and the suggest where the arcs intersect (Q).

PQ âŠ¥ AB

use your compass and ruler to draw a perpendicular at the given point on every line:

## Bisecting angles

Angles are developed when any two lines meet. Us use degrees (°) to measure up angles.

### Measuring and also classifying angles

In the figures below, every angle has actually a number from 1 come 9.

usage a protractor to measure up the sizes of all the angle in each figure. Create your answers on every figure.

(hat1 = ext_______ ^circ)

(hat1 + hat2 = ext_______ ^circ)

(hat1 + hat4 = ext_______ ^circ)

(hat2 + hat3 = ext_______ ^circ)

(hat3 + hat4 = ext_______ ^circ)

(hat1 + hat2 + hat4 = ext_______ ^circ)

(hat1 + hat2 + hat3 + hat4 = ext_______ ^circ)

(hat6 = ext_______ ^circ)

(hat7 + hat8 = ext_______ ^circ)

(hat6 + hat7 + hat8 = ext_______ ^circ)

(hat5 + hat6 + hat7 = ext_______ ^circ)

(hat6 + hat5 = ext_______ ^circ)

(hat5 + hat6 + hat7 + hat8 = ext_______ ^circ)

(hat5 + hat6 + hat7 + hat8 + hat9 = ext_______ ^circ)

beside each price above, compose down what kind of edge it is, namely acute, obtuse, right, straight, reflex or a revolution.

### Bisecting angle without a protractor

check out through the adhering to steps.

Step 1

Place the compass on the crest of the angle (point B). Draw an arc across each eight of the angle.

Step 2

Place the compass on the suggest where one arc crosses an arm and draw an arc within the angle. Without an altering the compass width, repeat because that the other arm so that the two arcs cross.

Step 3

Use a leader to sign up with the vertex to the point where the arcs crossing (D).

DB is the bisector that (hatABC).

use your compass and also ruler come bisect the angles below.

You could measure each of the angles with a protractor to inspect if you have bisected the provided angle correctly.

## Constructing special angles there is no a protractor

### Constructing angles of and

check out through the complying with steps.

Step 1

Draw a line segment (JK). V the compass on suggest J, attract an arc throughout JK and up over over point J.

Step 2

Without transforming the compass width, move the compass to the point where the arc crosses JK, and also draw an arc that crosses the very first one.

Step 3

Join allude J come the point where the two arcs accomplish (point P). (hatPJK) = 60°

When friend learn an ext about the properties of triangle later, you will know whythe technique above create a 60° angle. Or deserve to you already work this the end now? (Hint: What execute you know about equilateral triangles?)

construct an edge of 60° at point B below. Bisect the edge you constructed. carry out you an alert that the bisected angle consists of 2 30° angles? extend line segment BC come A. Then measure the angle nearby to the 60° angle.

What is the size?

The 60° angle and also its surrounding angle include up to

### Constructing angles of and

construct an angle of 90° at allude A. Go back to section 10.2 if you require help. Bisect the 90° angle, to produce an edge of 45°. Go ago to ar 10.3 if you need help.

Challenge

Work in your exercise book. Shot to build the following angles without using a protractor: 150°, 210° and also 135°.

## Constructing triangles

In this section, you will learn how to build triangles. Girlfriend will need a pencil, a protractor, a ruler and a compass.

A triangle has three sides and also three angles. We have the right to construct a triangle once we recognize some the its measurements, the is, the sides, its angles, or few of its sides and angles.

### Constructing triangles

Constructing triangles once three sides space given

check out through the complying with steps. They describe how to construct ( riangle ABC) with side lengths that 3 cm, 5 cm and also 7 cm.

Step 1

Draw one side of the triangle making use of a ruler. That is often simpler to start with the longest side.

Step 2

Set the compass width to 5 cm. Draw an arc 5 cm away from allude A. The 3rd vertex of the triangle will certainly be somewhere follow me this arc.

Step 3

Set the compass width to 3 cm. Attract an arc from suggest B. Note where this arc crosses the first arc. This will certainly be the third vertex of the triangle.

Step 4

occupational in your exercise book. Monitor the steps over to build the complying with triangles: ( riangle ABC) with sides 6 cm, 7 cm and also 4 centimeter ( riangle KLM) through sides 10 cm, 5 cm and also 8 cm ( riangle PQR) through sides 5 cm, 9 cm and 11 centimeter

Constructing triangle when certain angles and also sides are given

use the unstable sketches in (a) to (c) listed below to construct exact triangles, using a ruler, compass and protractor. Do the building next to each turbulent sketch. The dotted lines show where you need to use a compass to measure the length of a side. usage a protractor to measure the dimension of the provided angles. construct ( riangle ABC), with two angle and one next given.

build a ( riangle KLM), through two political parties andan edge given.

construct right-angled ( riangle PQR), through thehypotenuse and one various other side given.

measure the lacking angles and also sides of each triangle in 3(a) to (c) ~ above the ahead page. Write the dimensions at your completed constructions. compare each that your created triangles in 3(a) come (c) through a classmate"s triangles. Room the triangles exactly the same?

Challenge

build these triangles: ( riangle extSTU), with three angles given: (S = 45^circ), (T = 70^circ) and (U = 65^circ) . ( riangle extXYZ), through two sides and also the edge opposite one of the political parties given: (X = 50^circ) , (XY = 8 ext cm) and (XZ = 7 ext cm). have the right to you find more than one equipment for each triangle above? describe your result to a classmate.

## Properties of triangles

The angles of a triangle can be the exact same size or different sizes. The sides of a triangle deserve to be the same size or various lengths.

### Properties of it is intended triangles

build ( riangle ABC) alongside its rough map out below. Measure and also label the size of all its sides and angles.

Measure and write down the size of the sides and also angles of ( riangleDEF) below.
Both triangles in concerns 1 and also 2 are dubbed equilateral triangles. Talk about with a classmate if the adhering to is true because that an equilateral triangle: every the sides room equal. every the angles room equal come 60°.

### Properties of isosceles triangles

construct ( riangle extDEF) through (EF = 7 extcm, ~hatE = 50^circ ) and also (hatF = 50^circ).

Also build ( riangle extJKL) through (JK = 6 extcm,~KL = 6 extcm) and (hatJ=70^circ).

Measure and label all the sides and also angles of each triangle. Both triangles over are called isosceles triangles. Talk about with a classmate whether the complying with is true for an isosceles triangle: only two sides space equal. just two angles are equal. The 2 equal angles space opposite the two equal sides.

### The amount of the angles in a triangle

Look in ~ your created triangles ( riangle extABC,~ riangle extDEF ) and also ( riangle extJKL) above and top top the ahead page. What is the amount of the 3 angles each time? go you uncover that the sum of the interior angles of every triangle is 180°? execute the complying with to check if this is true for various other triangles. ~ above a clean sheet of paper, construct any kind of triangle. Label the angles A, B and also C and also cut out the triangle.
nicely tear the angle off the triangle and also fit them next to one another. notice that (hatA + hatB + hatC = ext______^circ)

A square is any type of closed shape with 4 straight sides. We classify quadrilaterals according to their sides and angles. We keep in mind which sides room parallel, perpendicular or equal. We additionally note i beg your pardon angles space equal.

Measure and also write down the size of every the angles and also the lengths of all the sides of each square below.

Square

Rectangle

Parallelogram

Rhombus

Trapezium

Kite

use your answers in concern 1. Ar a Ã¢ÂœÂ“ in the exactly box below to display which home is correct for each shape.

Opposite sides are equal

All sides space equal

Two bag of nearby sides room equal

Opposite angles are equal

All angles are equal

 Properties Parallelogram Rectangle Rhombus Square Kite Trapezium Only one pair that sides space parallel Opposite sides room parallel

### Sum of the angle in a quadrilateral

include up the four angles the each quadrilateral on the vault page. What do you notice about the sum of the angle of every quadrilateral? did you uncover that the amount of the interior angles of every quadrilateral amounts to 360°? perform the adhering to to inspect if this is true for various other quadrilaterals. ~ above a clean sheet of paper, usage a ruler to construct any type of quadrilateral. brand the angles A, B, C and also D. Reduced out the quadrilateral. neatly tear the angles off the quadrilateral and fit them beside one another. What carry out you notice?

You learnt how to build perpendicular currently in section 10.2. If friend know exactly how to construct parallel lines, girlfriend should have the ability to construct any type of quadrilateral accurately.

### Constructing parallel present to draw quadrilaterals

Step 1

From line segment AB, note a allude D. This allude D will be ~ above the line that will be parallel to AB. Attract a heat from A through D.

Step 2

Draw an arc from A that crosses advertisement and AB. Keep the very same compass width and also draw an arc from allude D together shown.

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Step 3

Set the compass width to the distance between the 2 points whereby the very first arc crosses advertisement and AB. From the allude where the second arc crosses AD, attract a 3rd arc to cross the second arc.