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secondary 4 | E Maths
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Royal Lim
Royal Lim

secondary 4 chevron_right E Maths chevron_right Singapore

How to do q4 !! Thanks for help in advance!!

Date Posted: 11 months ago
Views: 34
11 months ago
∠COB = ∠BAO + ∠ABO (ext angle = sum of 2 int opp angles)

= 90° + x°

OB = OC (both are radius of the same cir cle)
Since D is midpoint of BC,


OD is common to △BOD and △ COD

So △ BOD and △COD are congruent (SSS)

So ∠BOD = ∠ COD

∠COB = ∠COD + ∠COB
(90 + x)° = 2∠COD (since ∠BOD = ∠ COD)
∠COD = (90 + x)° ÷ 2
= (45 + ½x)°
Royal Lim
Royal Lim
11 months ago

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Eric Nicholas K
Eric Nicholas K's answer
4399 answers (Tutor Details)
The challenge in this question is to express the angles in terms of x. So essentially, you are finding the answer in terms of x rather than regular numbers. Usual rules for circles and triangles continue to apply.