Trigonometry Lesson 3
ADVERTISEMENT
1
2
3Trigonometry lesson 3
Same shape triangles
Lesson overview
In this activity students use practical measurement skills and ratio calculations to find a
pattern linking the ratio of sides of a triangle with the angles. This lesson is designed to
develop the concepts of sine, cosine and tangent ratios of angles.
Students should:
Grouping
1. have a knowledge of the concept of
Step 1: whole class
ratio
2. have the ability to convert fractions to
Step 2: groups of 3 or 4 students
decimals using a calculator to 3 decimal
places
Step 3: whole class
3. be able to measure the length of sides
of triangles to the nearest millimetre
Outcomes
Individual student materials
• pencil
• ruler
MS5.1.2 (p 139) Applies trigonometry to
• calculator
solve problems (diagrams given) including
• scrap paper
those involving angles of elevation and
depression
Group materials
• one set of triangles per group. Triangle
WMS5.1.4 Explains and verifies
sheets A-G should be photocopied onto
mathematical relationships
coloured cardboard. Carefully cut out the
triangles and place each set (8 triangles
in a set) into plastic bags.
• One Calculating ratios for similar
triangles worksheet per group
Class materials
• Three large charts (enlarge to A3) – one
for each ratio (opp/hyp, adj/hyp and
opp/adj) - for a class graph
• At this point only label the graphs with
the ratios – introduce the trig names sin,
cos and tan at the end of this lesson
Step 1
Questioning
• Show the students a large right-angled
• What is the hypotenuse of a right-angled
triangle with one angle marked
triangle? Where do you find it?
• What is ratio?
• What happens to the opp/hyp ratio when
hyp
opp
the angle is large?
• What happens to the opp/hyp ratio when
the angle is small?
adj
• Remind the students about the
hypotenuse (from Pythagoras’ theorem)
and show them the opposite and
Stage 5
Page 1 of 3
Mathematics Unit, Curriculum K–12 Directorate
Trigonometry
NSW Department of Education and Training
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Education