KnowledgeBoat Logo
|

Mathematics

Arrange the sides of △ BOC in descending order of their lengths. BO and CO are bisectors of angles ABC and ACB respectively.

Arrange the sides of △ BOC in descending order of their lengths. BO and CO are bisectors of angles ABC and ACB respectively. Inequalities, Concise Mathematics Solutions ICSE Class 9.

Triangles

12 Likes

Answer

From figure,

DAC is a straight line.

∴ ∠DAB + ∠BAC = 180°

⇒ 137° + ∠BAC = 180°

⇒ ∠BAC = 180° - 137° = 43°.

EBC is a straight line.

∴ ∠EBA + ∠ABC = 180°

⇒ 106° + ∠ABC = 180°

⇒ ∠ABC = 180° - 106° = 74°.

In △ ABC,

By angle sum property of triangle,

⇒ ∠ABC + ∠BAC + ∠ACB = 180°

⇒ 74° + 43° + ∠ACB = 180°

⇒ 117° + ∠ACB = 180°

⇒ ∠ACB = 180° - 117° = 63°.

Since, OB is the bisector of angle ABC.

∴ ∠OBC = ABC2=74°2\dfrac{∠ABC}{2} = \dfrac{74°}{2} = 37°.

Since, OC is the bisector of angle ACB.

∴ ∠OCB = ACB2=63°2\dfrac{∠ACB}{2} = \dfrac{63°}{2} = 31.5°.

In △ OBC,

By angle sum property of triangle,

⇒ ∠OBC + ∠OCB + ∠BOC = 180°

⇒ 37° + 31.5° + ∠BOC = 180°

⇒ 68.5° + ∠BOC = 180°

⇒ ∠BOC = 180° - 68.5° = 111.5°

∴ ∠BOC > ∠OBC > ∠OCB

∴ BC > CO > BO (If two angles of a triangle are unequal, the greater angle has the greater side opposite to it.)

Hence, sides of triangle BOC in descending order are BC > CO > BO.

Answered By

8 Likes


Related Questions