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In the adjoining figure, not drawn to the scale, AB is a tower and two objects C and D are located on the ground, on the same side of AB. When observed from the top A of the tower, their angles of depression are 45° and 60°. Find the distance between the two objects, if the height of the tower is 300 m. Give your answer to the nearest meter.

In the adjoining figure, not drawn to the scale, AB is a tower and two objects C and D are located on the ground, on the same side of AB. When observed from the top A of the tower, their angles of depression are 45° and 60°. Find the distance between the two objects, if the height of the tower is 300 m. Give your answer to the nearest meter. Heights and Distances, ML Aggarwal Understanding Mathematics Solutions ICSE Class 10.

Heights & Distances

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Answer

From figure,

In the adjoining figure, not drawn to the scale, AB is a tower and two objects C and D are located on the ground, on the same side of AB. When observed from the top A of the tower, their angles of depression are 45° and 60°. Find the distance between the two objects, if the height of the tower is 300 m. Give your answer to the nearest meter. Heights and Distances, ML Aggarwal Understanding Mathematics Solutions ICSE Class 10.

∠ACB = ∠EAC = 45° (Alternate angles are equal)
∠ADB = ∠EAD = 60° (Alternate angles are equal)

Considering right angled △ABC, we get

tan 45°=ABCB1=300CBCB=300\Rightarrow \text{tan 45°} = \dfrac{AB}{CB} \\[1em] \Rightarrow 1 = \dfrac{300}{CB} \\[1em] \Rightarrow CB = 300

Considering right angled △ADB, we get

tan 60°=ABDB3=300DBDB=3003DB=173.2\Rightarrow \text{tan 60°} = \dfrac{AB}{DB} \\[1em] \Rightarrow \sqrt{3} = \dfrac{300}{DB} \\[1em] \Rightarrow DB = \dfrac{300}{\sqrt{3}} \\[1em] \Rightarrow DB = 173.2

Distance between two objects (CD) = CB - DB = 300 - 173.2 = 126.8.

Rounding off to nearest meter CD = 127 m.

Hence, the distance between two objects = 127 meters.

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