Transcript Slide 1

General Mathematic
(HSC)
Bearings
Stage 6 - Year 12
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Bearing (1/4)
•Bearings are used to describe direction.
• Compass bearings have four main NW
directions and four middle
W
directions
• True Bearings are more
specific, using a 3-digit angle
clockwise from North.
Practice 1
Web
Practice 2
Web
SW
N
NE
E
S
SE
Practice 3
Web
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Bearing Ex 1 (2/4)
Ship A is 17km west of a lighthouse L.
Ship B is due south of the lighthouse L.
Ship B is SE of ship A.
N
Calculate distance d from Ship A to ship B.
A.
45o
Cos 45o = 17
d
d = 17 ÷ Cos 45o
≈ 24 km
17 km
.L
d
.B
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Bearing Ex 2 (3/4)
A Ship sails for 20 km on a bearing of 130o.
How far south is the ship from its starting point?
130o
d
50o
20 km
Cos 50o = d
20
d = 20 x Cos 50o
≈ 12.9 km
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Bearing Ex 3 (4/4)
Mary walks 3.4 km east, then 1.3 km south.
Find Mary’s bearing from her starting position.
90o
θo
3.4 km
Tan θo = 1.3
3.4
θo = Tan-1 ( 1.3 )
3.4
≈ 21o
1.3 km
Bearing = 90o + 21o
= 111o
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