Lesson
Introduction to Trigonometry
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maman
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• Slide 1
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Introduction to Trigonometry

Text
• Slide 2
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Objectives

• Identify the sides of right-angled triangles

• Calculate complementary angle of right-angled triangles

• Slide 3
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History

The word trigonometry comes from the Greek words trigon (triangle) and metria (measurement).

Originally trigonometry was used as an aid in the study of astronomy.

• Slide 4
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Name Sides in Right-Angled Triangles

• The Hypotenuse

• The opposite side

• Slide 5
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Complementary Angles

• The three angles in any triangle add to 180°.

• Since one angle in a right-angled triangle measures 90°, the other two angles must add to 90° to make up the 180°.

• The two acute angles in any right-angled triangle are complementary angles (ie add to 90°).

• Slide 6
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Label Sides

• Use the two CAPITAL letters at its ends.

• Use one lower case letter which matches the opposite vertex (corner).

• Side GH can be called f.

• Question 7
30 seconds
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Q.

$\theta$  is ...

LM

LN

MN

• Question 8
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Q.

The hypotenuse is ...

LM

LN

MN

• Question 9
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Q.

What is the name given to the longest side of a right-angled triangle?

Hypotenuse

Opposite

• Question 10
30 seconds
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Q.

The side opposite to angle

$\theta$  is ...

LM

LN

MN

• Question 11
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Q.

The side ‘next to’ the marked angle is called:

Hypotenuse

Touching

• Question 12
30 seconds
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Q.

Which of the following has the longest side?

LM

LN

MN

• Question 13
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Q.

What is the opposite angle to the side with length 12 m?

angle A

angle B

angle C

• Question 14
30 seconds
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Q.

Which angle must be the right angle for this triangle?

angle A

angle B

angle C

• Question 15
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Q.

Complementary angles add together to give:

900

1800

3600

• Question 16
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Q.

What is the size of angle P?

900

240

660

760

• Question 17
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Q.

What is the size of the missing angle in this triangle?

200

300

900

1600

• Question 18
60 seconds
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Q.

Insert a capital letter to make this statement true.

Side opposite angle B = Side adjacent to angle ...

A

B

C

• Question 19
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Q.

Choose the response that correctly completes this statement.

The side adjacent to angle R is also:

opposite angle P

opposite angle R

• Question 20
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Q.

What is the complement of 500?

900

500

400

30

• Question 21
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Q.

In which of these diagrams are all sides correctly named, with respect to angle P?