The perimeter of a rhombus is 40 cm. If the length of one

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The perimeter of a rhombus is 40 cm. If the length of one of its diagonals be 12 cm, the length of the other diagonal is

Using Rule 12,
If d₁ and d₂ be the diagonals of a rhombus, we have
Perimeter = 4 × side
= 2√d₁² + d₂²

	∵ side =	1	√d₁² + d₂²
		2

⇒ 40 = 2√12² + d₂²
⇒ 20 = √144 + d₂²
⇒ 144 + d₂² = 20² = 400
⇒ d₂² = 400 – 144 = 256
⇒ d₂ = √256
= 16 cm.