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Mathematics

Assertion (A) : One of the diagonals of rhombus is equals to one of its side. The angles of a rhombus are 60°, 120°, 60°, 120°.

Reason (R) : All the sides of a rhombus are equal.

  1. Both A and R are correct, and R is the correct explanation for A.

  2. Both A and R are correct, and R is not the correct explanation for A.

  3. Statement 1 is true, and statement 2 is false.

  4. Statement 1 is false, and statement 2 is true.

Quadrilaterals

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Answer

By property,

All the sides of a rhombus are equal.

So, reason (R) is true.

ABCD is the rhombus and AC is the diagonal such that AC = AB.

One of the diagonals of rhombus is equals to one of its side. The angles of a rhombus are 60°, 120°, 60°, 120°. Special Types Of Quadrilaterals, Concise Mathematics Solutions ICSE Class 8.

In triangle ABC,

⇒ AB = BC (Sides of rhombus are equal)

⇒ AB = AC (Given)

⇒ AB = AC = BC

So, triangle ABC is an equilateral triangle.

∴ ∠B = 60°, ∠BAC = 60° and ∠BCA = 60°.

In triangle ADC,

⇒ AD = CD (Sides of rhombus are equal)

⇒ AD = AC (Since, AB = AC and AB = AD)

⇒ AD = CD = AC

So, triangle ADC is an equilateral triangle.

∴ ∠D = 60°, ∠DAC = 60° and ∠DCA = 60°

⇒ ∠A = ∠BAC + ∠DAC = 60° + 60° = 120°.

⇒ ∠C = ∠BCA + ∠DCA = 60° + 60° = 120°.

Hence, the angles of a rhombus are 60°, 120°, 60°, 120°.

So, assertion (A) is true.

∴ Both A and R are correct, and R is not the correct explanation for A.

Hence, option 2 is the correct option.

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