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C2 the sine and cosine rules.
If you know one side, the opposite angle and one other value use the sine rule.
If you know all 3 sides use the cosine rule.
If you know 2 sides and the angle between them use the cosine rule.
The ambiguous case
Two angles between 0 and 180 degrees can have the same sine.
This means two different triangles with different areas can be drawn from
the same information.
In general if x= y degrees then x also equals 180 y.
These questions will ask for values rather than value.
WJEC C2 May 09 qu3.
The triangle ABC is such that AB = 16 cm, AC = 9 cm and ABC = 23°.
(a) Find the possible values of ACB. Give your answers correct to the nearest degree. 
(b) Given that BAC is an acute angle, find
(i) the size of BAC, giving your answer correct to the nearest degree,
18013623= 21 degrees
(ii) the area of triangle ABC, giving your answer correct to one decimal place. 
Using the cosine rule for sides:
=25.8 cm^2 1dp