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Side BA is produced upto point D and side BC upto point E such that ∠DAC = 110° and ∠ACE = 125°. Then the largest side of the triangle ABC is

Side BA is produced upto point D and side BC upto point E such that ∠DAC = 110° and ∠ACE = 125°. Then the largest side of the triangle ABC is. Isosceles Triangles, Concise Mathematics Solutions ICSE Class 9.
  1. AB

  2. BC

  3. AC

  4. none of these

Triangles

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Answer

From figure, ∠DAC and ∠BAC forms linear pair.

⇒ ∠DAC + ∠BAC = 180°

⇒ 110° + ∠BAC = 180°

⇒ ∠BAC = 180° - 110°

⇒ ∠BAC = 70°

Similarly, ∠ACE and ∠ACB forms linear pair.

⇒ ∠ACE + ∠ACB = 180°

⇒ 125° + ∠ACB = 180°

⇒ ∠ACB = 180° - 125°

⇒ ∠ACB = 55°

In ΔABC, according to angle sum property,

⇒ ∠ABC + ∠ACB + ∠BAC = 180°

⇒ ∠ABC + 55° + 70° = 180°

⇒ ∠ABC + 125° = 180°

⇒ ∠ABC = 180° - 125°

⇒ ∠ABC = 55°

As we know that the side opposite to the largest angle in a triangle is the longest side.

Since, ∠BAC is the largest angle of the triangle.

So, BC is the largest side of the triangle ABC.

Hence, option 2 is the correct option.

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