Area of a triangle
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Transcript of Area of a triangle
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Objective: to be able to calculate the area of a triangle using trigonometry (Grade A)
By the end of the lesson:All: will be to identify when to find the area of a triangle using
Most: will be able to calculate the area of a triangle using the formula
Some: will be to calculate GCSE area of a triangle problems using
Trigonometry
(Up to Grade A*)
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StarterCalculate the area of the following
shapesGreen Red
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Starter - Answers
Green Red
Area = 24cm2
Area = 2.4mm2
Area = 35cm2
Area = 50cm2
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Calculate the Area of this triangle
What do we need to know to calculate the area of this triangle?
Can we calculate this?
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What can we use to find h?
×8 ×8
This is found by trig
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How the ABC’s work
A
C
B
a
c
b
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A
C
B
a
c
b
The Formula
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Formula
Page
You do need to learn this
as its no longer given.
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Task 1For which of the following questions is it possible to find the area of the triangle using (Hint: look for an angle between 2 given
sides)
Extension: create your own example of a question that could solved using the formula we have learnt
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Task 1 - Solutions
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Examples
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Task 2 – Give your answers to 3 significant figures
Extension:
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Task 2 - Solutions
a = 9.58 cm2
b = 44.5 cm2
c = 26.2 cm2
d = 17.3 cm2
e = 63.3 cm2
f = 28.7 cm2
Extension
a = 202cm2
b = 72.2cm2
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In your own words
Explain how you calculate the area of a triangle using trigonometry?
Use the wordsAreaAngleSidesSine
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Finding missing side or angle given the area.
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Task 3 – Give your answers to 3 significant figures
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Task 3 - Solutions
a = 3.90 cm
b = 7.39 cm
x = 56.4o
y = 57.1o
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Task 4 – Past GCSE Questions
Complete the following past GCSE questions
There are green, amber and red sections
(Red Grade A*)(Green and Amber Grade A)
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Task 2 – Solutions
Green Amber Red
area = 19.31851653cm2
area = 19.3cm2 (3 s.f.)
area = 2068.319996m2
area = 2070m2 (3 s.f)
x = 9.118028228cm
x = 9.12cm (3 s.f.)
area = 10.87606829m2
area = 10.9m2 (3 s.f)
area = 1.771010916cm2
area = 1.78cm2 (3s.f.)
area = 119.3241659m2
area = 119m2 (3 s.f)
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Green 1
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Green 2
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Amber 1
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Amber 2
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Red 1
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Red 2
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To finish the lesson
In your own words, explain when you would apply
to calculate the area, missing angle or missing side
of a triangle.
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Further GCSE Questions
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