Transcript Slide 1

General Mathematic
(HSC)
Cosine Rule
Sides
Stage 6 - Year 12
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The Cosine Rule – Find a Side (1/2)
A
c
b
C
a
B
c2 = a2 + b2 – 2ab Cos C
b2 = a2 + c2 – 2ac Cos B
a2 = b2 + c2 – 2bc Cos A
To use the Cosine Rule – Area we need …
two sides and …
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the angle between them.
2
The Cosine Rule – Find a Side (2/2)
c
6
30o
7
c2 = a2 + b2 – 2ab Cos C
c2 = 62 + 72 – 2 x 6 x 7 x Cos 30
c = 62 + 72 – 2 x 6 x 7 x Cos 30
= 3.500552254
≈ 3.5
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