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Lines And Angles

Question
CBSEENMA9002410

In figure, ∠X = 62°, ∠XYZ = 54°. If YO and ZO are the bisectors of ∠XYZ and ∠XZY respectively of ∆XYZ, find ∠OZY and ∠YOZ.


Solution

In ∆XYZ,
∠XYZ + ∠YZX + ∠ZXY = 180°
| ∵ The sum of all the angles of a triangle is 180°
⇒ 54° + ∠YZX + 62° = 180°
⇒    116° + ∠YZX = 180°
⇒ ∠YZX = 180° - 116° = 64°    ...(1)
∵ YO is the bisector of ∠XYZ

therefore space angle XYO equals angle OYZ equals 1 half angle XYZ
space space space space space space space space space space space space space equals 1 half left parenthesis 54 degree right parenthesis equals 27 degree space space space space space space space space space space space space space space space space space space space space space space space space.... left parenthesis 2 right parenthesis
∵ ZO is the bisector of ∠YZX
therefore space space space space space angle XZO space equals angle OZY equals 1 half angle YZX
space space space space space space space space space space space space space space space space space space equals space 1 half left parenthesis 64 degree right parenthesis equals 32 degree space space space space space space space space space space space space space space space space space.. left parenthesis 3 right parenthesis
                                                   | Using (1)

In ∆OYZ,
∠OYZ + ∠OZY + ∠YOZ = 180°
|∵ The sum of all the angles of a triangle is 180°
⇒ 27° + 32° + ∠YOZ = 180°
| Using (2) and (3)
⇒ 59° + ∠YOZ = 180°
⇒    ∠YOZ = 180° - 59° = 121°.