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In the figure given below, D and E are mid-points of the sides AB and AC respectively. If BC = 5.6 cm and ∠B = 72°, compute

(i) DE

(ii) ∠ADE

In the figure, D and E are mid-points of the sides AB and AC respectively. If BC = 5.6 cm and ∠B = 72°, compute (i) DE (ii) ∠ADE. Mid-point Theorem, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Mid-point Theorem

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Answer

(i) Since, D and E are mid-points of the sides AB and AC respectively,

∴ DE is parallel to BC and DE = 12BC=12(5.6)\dfrac{1}{2}BC = \dfrac{1}{2}(5.6) = 2.8 cm. (By midpoint theorem)

Hence, DE = 2.8 cm.

(ii) Since, DE is parallel to BC.

∴ ∠ABC = ∠ADE (Corresponding angles)

⇒ ∠ADE = 72°.

Hence, ∠ADE = 72°.

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