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Mathematics

Find AD.

(i)

Find AD. Heights and Distances, Concise Mathematics Solutions ICSE Class 10.

(ii)

Find AD. Heights and Distances, Concise Mathematics Solutions ICSE Class 10.

Heights & Distances

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Answer

(i) From figure,

BE = CD = 20 m and DE = CB = 5 m.

In △ABE,

tan 32°=PerpendicularBase0.6249=AEBEAE=0.6249×BEAE=0.6249×20AE=12.498 m.\text{tan 32°} = \dfrac{\text{Perpendicular}}{\text{Base}} \\[1em] \Rightarrow 0.6249 = \dfrac{AE}{BE} \\[1em] \Rightarrow AE = 0.6249 \times BE \\[1em] \Rightarrow AE = 0.6249 \times 20 \\[1em] \Rightarrow AE = 12.498 \text{ m}.

AD = AE + DE = 12.498 + 5 = 17.498 ≈ 17.5 m.

Hence, AD = 17.5 meters.

(ii) We know that,

An exterior angle is equal to the sum of two opposite interior angles.

∴ ∠ACD = ∠ABC + ∠BAC

Also, ∠ABC = ∠BAC (As, angles opposite to equal sides are equal)

∴ ∠ACD = 2∠ABC

⇒ 2∠ABC = 48°

⇒ ∠ABC = 24°.

In △ABD,

sin 24°=PerpendicularHypotenuse0.4067=ADABAD=0.4067×ABAD=0.4067×30AD=12.20 m.\text{sin 24°} = \dfrac{\text{Perpendicular}}{\text{Hypotenuse}} \\[1em] \Rightarrow 0.4067 = \dfrac{AD}{AB} \\[1em] \Rightarrow AD = 0.4067 \times AB \\[1em] \Rightarrow AD = 0.4067 \times 30 \\[1em] \Rightarrow AD = 12.20 \text{ m}.

Hence, AD = 12.20 meters.

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