Sine Rule

All you need to know to do with Sine

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The use of Sine rule

Sine rule is used to work out the length of a side of a triangle or to work out an angle of a triangle.

However these rules arent required for right angled triangles.

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Sine rule

To use the Sine Rule you must break the triangle into letters. All the sides are given a lower case letter. a, b, c.All the angles are given a upper case letter A, B, C.The same letters must be opposite to each other eg. a is the side opposite angle A. Sine Rule = a/SinA = b/Sinb = c/Sinc.

(http://www.y-maths.co.uk/Image127.gif)

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Using the sine rule

Using the triangle in the earlier slide we can work out side 'a' (the opposite to angle 'A').

a/SinA = c/SinC

a/Sin45 = 10/Sin60

a = 10/Sin60 x Sin45

a = 8.16 cm

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Cosine

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