In each of the following figure , O is the centre of the circle . Find the size of each lettered angle :
Figures are given below
Answers
Answer:
(i) In the figure, AB is the diameter
and O is the centre of the circle ∠ CAB = 32°,
∠ ABD = 50° , ∠C = 90° (Angle in the semicircle)
By ∠ sum property of ∆
In ∆ABC, ∠C + ∠CAB + ∠ABC = 180°
⇒ 90° + ∠CAB + x = 180°
⇒ 32° + x = 180° – 90°
⇒ x = 90° – 32°
⇒ x = 58°
Similarly in right ∆ ADB
∠ADB = 90°
By ∠ sum property of ∆
∠ABD + ∠D + ∠BAD = 180°
⇒ 50° + 90° + ∠BAD = 180°
⇒ ∠y + 140° = 180°
⇒ ∠y = 180° – 140° = 40°
⇒ ∠y = 40°
ii) In the figure,
AC is the diameter of circle with centre O
∠DAC=37
AD || BC
∠ACB=∠DAC (Alternate angles)
Hence,
x=37
In Δ ABC,
∠B=90 (angle in semicircle)
By angle sum property of triangle, we get,
∠x+∠y+∠B=180
37 +∠y+90 =180
∠y=180−127
We get,
∠y=53
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