ML Agarwal Heights and distances class 10 Maths

There is a small island in between a river 100 metres wide. A tall tree stands on the island. P and Q are points directly opposite to each other on the two banks and in the line with the tree. If the angles of elevation of the top of the tree from P and Q are 300 and 450 respectively, find the height of the tree.

Solution: Width of the river PQ = 100 m B is the island and AB is the tree on it Angles of elevation from A to P and Q are 300 and 450 Consider AB = h PB = x BQ = 100 – x In right triangle APB tan θ...

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A man on the deck of a ship is 16 m above the water level. He observes that the angle of elevation of the top of a cliff is 450 and the angle of depression of the base is 300. Calculate the distance of the cliff from the ship and the height of the cliff. Solution:

Solution: Consider A as the man on the deck of a ship B and CE is the cliff AB = 16 m Angle of elevation from the top of the cliff = 450 Angle of depression at the base of the cliff = 300 Take CE =...

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In the adjoining figure, the angle of elevation of the top P of a vertical tower from a point X is 60 degree; at a point Y, 40 m vertically above X, the angle of elevation is 450. Find (i) the height of the tower PQ (ii) the distance XQ (Give your answer to the nearest metre)

Solution: Consider PQ as the tower = h XQ = YR = y XY = 40 m PR = h – 40 In right triangle PXQ tan θ = PQ/XQ Substituting the values tan 600 = h/y So we get √3 = h/y y = h/√3 ….. (1) In right...

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A vertical pole and a vertical tower are on the same level ground. From the top of the pole the angle of elevation of the top of the tower is 600 and the angle of depression of the foot of the tower is 300. Find the height of the tower if the height of the pole is 20 m.

Solution: Consider TR as the tower PL as the pole on the same level Ground PL = 20 m From the point P construct PQ parallel to LR ∠TPQ = 600 and ∠QPR = 300 Here ∠PRL = ∠QPR = 300 which are the...

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The angles of depression of the top and the bottom of an 8 m tall building from the top of a multi-storeyed building are 300 and 450 respectively. Find the height of tire multi-storeyed building and the distance between the two buildings, correct to two decimal places.

Solution: Consider AB as the height and CD as the building The angles of depression from A to C and D are 300 and 450 ∠ACE = 300 and ∠ADB = 450 CD = 8 m Take AB = h and BD = x From the point C...

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From two points A and B on the same side of a building, the angles of elevation of the top of the building are 300 and 600 respectively. If the height of the building is 10 m, find the distance between A and B correct to two decimal places.

Solution: In triangle DBC tan 600 = 10/BC Substituting the values √3 = 10/BC BC = 10/√3 In triangle DBC tan 300 = 10/ (BC + AB) Substituting the values 1/√3 = 10/[10/√3 + AB] By further calculation...

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The angle of elevation of a pillar from a point A on the ground is 450 and from a point B diametrically opposite to A and on the other side of the pillar is 600. Find the height of the pillar, given that the distance between A and B is 15 m.

Solution: Consider CD as the pillar of x m Angles of elevation of points A and B are 450 and 600 It is given that AB = 15 m Take AD = y DB = 15 – y In right triangle CAD tan θ = CD/AD Substituting...

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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 450 and 600. Find the distance between the two objects. If the height of the tower is 300. Give your answer to the nearest metre.

Solution: Consider CB = x and DB = y AB = 300 m In right triangle ACD tan θ = AB/CB Substituting the values tan 450 = 300/x 1 = 300/x So we get x = 300 m In right triangle ADB tan θ = AB/DB...

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From the top of a church spire 96 m high, the angles of depression of two vehicles on a road, at the same level as the base of the spire and on the same side of it are x0 and y0, where tan x0 = ¼ and tan y0 = 1/7. Calculate the distance between the vehicles.

Solution: Consider CH as the height of the church A and B are two vehicles which make an angle of depression x0 and y0 from C Take AH = x and BH = y In a right triangle CBH tan x0 = CH/AH = 96/y...

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A man observes the angles of elevation of the top of a building to be 300. He walks towards it in a horizontal line through its base. On covering 60 m the angle of elevation changes to 600. Find the height of the building correct to the nearest decimal place.

Solution: It is given that AB is a building CD = 60 m In triangle ABC tan 600 = AB/BC √3 = AB/BC So we get BC = AB/√3 ….. (1) In triangle ABD tan 300 = AB/BD 1/√3 = AB/ (BC + 60) By cross...

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An aeroplane when flying at a heigt of 3125 m from the ground passes vertically below another plane at an instant when the angles of elevation of the two planes from the same point on the ground are 300 and 600 respectively. Find the distance between the two planes at the instant

Solution: Consider the distance between two planes = h m It is given that AD = 3125 m, ∠ACB = 600 and ∠ACD = 300 In triangle ACD tan 300 = AD/AC Substituting the values 1/√3 = 3125/AC AC = 3125√3...

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(i) In the adjoining figure, the angle of elevation from a point P of the top of a tower QR, 50 m high is 600 and that of the tower PT from a point Q is 300. Find the height of the tower PT, correct to the nearest metre. (ii) From a boat 300 metres away from a vertical cliff, the angles of elevation of the top and the foot of a vertical concrete pillar at the edge of the cliff are 550 40’ and 540 20’ respectively. Find the height of the pillar correct to the nearest metre.

Solution: Consider CB as the cliff and AC as the pillar D as the boat which is 300 m away from the foot of the cliff BD = 300 m Angle of elevation of the top and foot of the pillar are 550 40’ and...

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The upper part of a tree broken by wind falls to the ground without being detached. The top of the broken part touches the ground at an angle of 380 30’ at a point 6 m from the foot of the tree. Calculate (i) the height at which the tree is broken. (ii) the original height of the tree correct to two decimal places.

Consider TR as the total height of the tree TP as the broken part which touches the ground at a distance of 6 m from the foot of the tree which makes an angle of 380 30’ with the ground Take PR = x...

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An electric pole is 10 m high. A steel wire tied to the top of the pole is affixed at a point on the ground to keep the pole upright. If the wire makes an angle of 450 with the horizontal through the foot of the pole, find the length of the wire.

Consider AB as the pole and AC as the wire which makes an angle of 450 with the ground. Height of the pole AB = 10 m Consider x m as the length of wire AC We know that sin θ = AB/AC Substituting the...

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