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Mathematics

In the given figure,

In the given figure, AC = CD. 2. AB > CD. 3. AB < CD. 4. none of these. Isosceles Triangles, Concise Mathematics Solutions ICSE Class 9.
  1. AC = CD

  2. AB > CD

  3. AB < CD

  4. none of these

Triangles

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Answer

Since, AB = AC.

∴ ∠ABC = ∠ACB = 70° (As angles opposite to equal sides of an isosceles triangle are equal.)

From figure,

⇒ ∠ACB + ∠ACD = 180° [Linear pairs]

⇒ 70° + ∠ACD = 180°

⇒ ∠ACD = 110°.

In △ACD,

⇒ ∠CAD + ∠ADC + ∠ACD = 180°

⇒ ∠CAD + 40° + 110° = 180°

⇒ ∠CAD + 150° = 180°

⇒ ∠CAD = 30°.

In △ACD,

∠ADC = 40°

∠CAD = 30°

∴ ∠ADC > ∠CAD

∴ AC > CD (As side opposite to greater angle is greater.)

Since, AB = AC,

∴ AB > CD.

Hence, option 2 is the correct option.

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