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secondary 4 | E Maths
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Aaron
Aaron

secondary 4 chevron_right E Maths chevron_right Singapore

Couldn’t find angle BAC

Date Posted: 4 years ago
Views: 291
Boy Mow Chau
Boy Mow Chau
4 years ago
hint:

this type of questions generally involve application of sine rule and cosine rule.

(i)
… from bearing of B from A, what is bearing of A from B?
… from bearing of A from B, and bearing of C from B, what is angle ABC?
… thereafter, use AB, BC and angle ABC, and
apply ____?____ rule to find AC

(ii)
… use AC (from (i)), BC and angle ABC, and
apply ___?____ rule to find angle BAC.
Boy Mow Chau
Boy Mow Chau
4 years ago
after trying out to calculate the actual answers, found that there is a "possible complication" for part (ii), therefore have given the detail solution with explanation of the "possible complication" below.

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Boy Mow Chau
Boy Mow Chau's answer
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Boy Mow Chau
Boy Mow Chau
4 years ago
for part (ii), can use either method (b) or (c).

if use method (c), and if the unknown angle is obtuse, cos-1() will still directly give the correct angle.