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secondary 2 | Maths
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LYY
LYY

secondary 2 chevron_right Maths chevron_right Singapore

Please help me solve for angles ABY and CDY. Thanks!

Date Posted: 3 years ago
Views: 194
Shawn
Shawn
3 years ago
Is ABCD a square, given in the question?
J
J
3 years ago
I assume ABCD is a square.

So AB = BC = CD = AD and the 4 angles are all right angles (90°)

AC is the diagonal of the square, and it divides the square into 2 isosceles right-angled triangles ABC and ADC.

∠CAB = ∠BCA = 45° , they are base angles of the same isosceles triangle since AB = BC

( Or (180° - 90°)/2 = 45°)


∠YAB = ∠CAB - 19°
= 45° - 19°
= 26°

Since AB = AY, triangle ABY is isosceles
∠ABY = ∠AYB (base angles of the same isosceles triangle)

∠ABY = (180° - ∠YAB)/2

= (180° - 26°)/2

= 154° / 2

= 77°
J
J
3 years ago
And since AB = AY and AB = AD,

Then AY = AD

So triangle AYD is also isosceles.

∠AYD = ∠ADY (base angles of the same isosceles triangle)

∠DAY = ∠DAC + ∠ CAY
= 45° + 19°
= 64°

∠AYD = (180° - 64°)/2 = 58°

∠CDY = ∠ADC - ∠AYD
= 90° - 58°
= 32°
J
J
3 years ago
Edited
Shawn
Shawn
3 years ago
The working is correct, but 90-58=32. :)
J
J
3 years ago
Already edited 7 mins ago. Your app still showing 22°?
Shawn
Shawn
3 years ago
Yes still 22, even after seeing this message.
J
J
3 years ago
Maybe your app needs an update or reinstall. It's showing 32 online as well in addition to app

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Shawn
Shawn's answer
47 answers (A Helpful Person)
1st
Drawing on the diagram what is already known is a useful technique, e.g the equal lengths, the angles found.