Using Trigonometry to find missing angles

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  • Created by: Rachel
  • Created on: 25-03-09 10:40

Missing angles

The Hypotenuse of a right-angled triangle is the longest side.

The Opposite is the side opposite the angle we want to find.

The Adjacent is the side next to the angle.

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If we know 2 sides of a right-angled triangle we can use Trigonometry to workout the angles.If we know the Opposite and Hypotenuse we use sine to find the angle.

For example:If the Opp=3cm and Hyp= 5cm We find the angle (a) we want by using the equation.

Sin a=

Opposite/Hypotenuse = 3/5 = 0.6

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Sin= Opp/Hyp

Cos= Adj/Hyp

Tan= Opp/Adj


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Rearrange the equation to read like the folowing example:

12/13= 0.923

a= Cos-1 0.923

a= 22.6 (This is the angle)

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