1. Ch 4: Trigonometry 4D: Bearings

2. True Bearings • Important in navigation as used to communicate direction • True bearings (oT) are measured clockwise from due north. • Usually written using 3 digits (i.e. S E 135O) • Opposite directions differ by 180o

3. Example (pg. 9) N Find the True Bearing for point A, B, C & D D A 90o – 35o = 055o A = B = C = D = 70o 35o 90o+45o = 135o E 30o W 45o O 270o-30o = 240o C 360o-20o = 340o B S

4. Example (pg. 10) N N How far east is the person from their original position? W W E E STEP 1: Draw Triangle S S 10km 10km 30o Xcm 60o 15km STEP 2: Use SOH CAH TOA to find x Xcm x = 10cos60 x = 5km

5. Example (pg.10) N N How far north is the person from their original position? W W E E STEP 1: Draw Triangle 10km S S Xcm 30o 10km Xcm 30o STEP 2: Use SOH CAH TOA to find x 15km x = 10cos30 x = 8.66km Total distance = 15km +8.66km = 23.66km

6. Example (pg.11) N N Find how far east is the ship from its starting point, correct to two decimal places. W W E E Xcm STEP 1: Draw Triangle 30o S S 5km 11km 90o Xcm 30o STEP 2: Use SOH CAH TOA to find x 11km x = 11cos30 x = 9.526km

7. Example (pg.11) N N Find how far east is the ship from its starting point, correct to two decimal places. W W E E STEP 1: Draw Triangle S S 5km 11km 60o 90o Xcm 30o 11km STEP 2: Use SOH CAH TOA to find x Xcm x = 11cos60 x = 5.5km Total distance = 5km +5.5km = 10.5km

8. Question Ex 4D 4.4 Level 1: 2, 4-6 Level 2: 2 ace, 5, 6, 8, 9 Level 3: 2 c e, 6, 9 , 11, 13