Page 121 - Math SL HB Sem 1

CIRCULAR FUNCTIONS AND TRIGONOMETRY

The cosinc rule

For any triangle ABC,
:
a2 b' + c2 - 2bc cosA

b2 :a2 +c2 - 2accosB

c'=at +b']- 2abcosC

The cosine rule is used to solve a (non-righrangled) triangle if we are given
. the lengths of its three sides
o the lengths of two sides and the measure ofthe included angle

:
Example l: In triangle ABC if a = 12 cm, b: 20 cm and c 14 cm, finrl
A, B and C.

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