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#### Trigonometry

##### BEARINGS
• The bearing of a point B from another point A is:
• an angle measured from the north at A.
• in a clockwise direction.
• written as a three-figure number (i.e., 000° to 360°)
• For example, the bearing of B from A is 050°
##### PYTHAGORAS THEOREM

• To find the hypotenuse, c: c2 = a2 + b2
• To find one of the shorter sides:
• a2 = c2 – b2
• b2 = c2 – a2
• Angle of elevation: is the angles above the horizontal line.
• Angle of depression: is the angle below the horizontal line.
• Area of a triangle = ab/2 sin c
• Ratios
• Right angled Triangles:
• sin x = opposite/hypotenuse [SOH]
• cos x = adjacent/hypotenuse [CAH]
• tan x = opposite/adjacent [TOA]
• Sine Rule
• a/sin a = b/sin b = c/sin c
• One pair of information needed.
• Cosine Rule
• To find the angle when given 3 sides: cos a = (b2 + c2 – a2)/2bc
• To find a side when given the angle and two sides: a2 = b2 + c2 – 2bc cos a

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