Jackson Wan's answer to rei's Secondary 3 E Maths Singapore question.
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i) Using Sine rule,
BD/sin75 = AB/sin52 =49m/sin52
solve for length BD.
ii) Similarly solve for AD to find length AC=CD+DA
Use Cosine rule CB^2 = CA^2+49^2-2*AC*AB*Cos(75)
Solve for length CB
Find angle ACB using sine rule.
Draw a line pointing North passing through point B.
Bearing of C from B = 360deg-(180deg-angleACB)= 180deg+angleACB
b)Imagine right angle triangle with height 20m and base length = BD. Find the hypothenuse (E) using Pythagorean Theorem. E/sin90 = 20/sin(angle of depression)
Solve for angle of depression.
BD/sin75 = AB/sin52 =49m/sin52
solve for length BD.
ii) Similarly solve for AD to find length AC=CD+DA
Use Cosine rule CB^2 = CA^2+49^2-2*AC*AB*Cos(75)
Solve for length CB
Find angle ACB using sine rule.
Draw a line pointing North passing through point B.
Bearing of C from B = 360deg-(180deg-angleACB)= 180deg+angleACB
b)Imagine right angle triangle with height 20m and base length = BD. Find the hypothenuse (E) using Pythagorean Theorem. E/sin90 = 20/sin(angle of depression)
Solve for angle of depression.
Date Posted:
2 years ago
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