The Area of a Triangle

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The Area of a Triangle
How do we calculate the area of triangle ABC?
The base and height in the above formula must be
at right angles (or perpendicular).
But we will not always know a perpendicular
height. In this case there is a second formula we
can use
Area ½absinC
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Example 1
Find the area of this field in hectares.
Area ½absinC
½ ? 413 ? 234 ? sin68
4480245m2
448ha
Remember 1 hectare
10 000m2
10 000m2
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Example 2
Find the area of ?PQR, if P 56, q 236m and
r 436m.
Draw a diagram first.
Label diagram.
Area ½qrsinP
½ ? 236 ? 436 ? sin56
42652m2
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Todays work
Exercise 6C Pg 180 1ad, 2, 3