This page 10th samacheer kalvi math solution for exercise 7.2 part 7 is going to provide you solution for every problems that you find in the exercise no 7.2

**Question 17 :**

From the top and foot of a 40 m high tower, the angles of elevation of the top of a lighthouse are found to be 30° and 60° respectively. Find the height of the lighthouse. Also find the distance of the top of the lighthouse from the foot of the tower.

**Solution :**

AB = x m and BD = 40 m

In triangle ABC :

∠ACB = 30°

tan θ = opposite side/Adjacent side

tan 30° = AB/BC

1/√3 = x/BC

BC = x√3 ----(1)

In triangle ADE :

∠AED = 60°

tan θ = opposite side/Adjacent side

tan 60° = AD/DE

√3 = (x + 40)/DE

DE = (x + 40)/√3 ---->(2)

(1) = (2)

x√3 = (x + 40)/√3

3 x = x + 40

3x - x = 40

2x = 40

x = 20

Height of the tower = 40 + 20 = 60 m

**Question 18 :**

The angle of elevation of a hovering helicopter as seen from a point 45 m above a lake is 30° and the angle of depression of its reflection in the lake, as seen from the same point and at the same time, is 60°. Find the distance of the helicopter from the surface of the lake.

**Solution :**

From the given information, we can draw a rough diagram

In a right triangle FAE :

tan θ = opposite side/Adjacent side

tan 30° = FE/AE

1/√3 = (h-45)/AE

AE = (h - 45) √3 ----(1)

In right triangle ACE :

tan θ = opposite side/Adjacent side

tan 60° = EC/AE

√3 = (ED+DC)/AE

√3 = (45+h)/AE

AE = (45 + h)/√3----(2)

(1) = (2) (BC = AD)

(h - 45) √3 = (45 + h)/√3

3(h - 45) = 45 + h

3h - 135 = 45 + h

2h = 45 + 135

2h = 180

h = 90

Hence the distance of the helicopter from the surface of the lake is 90 m.

After having gone through the stuff given above, we hope that the students would have understood "10th samacheer kalvi math solution for exercise 7.2 part 7".

Apart from the stuff given above, if you want to know more about "10th samacheer kalvi math solution for exercise 7.2 part 7", please click here

Apart from the stuff given in this section, if you need any other stuff in math, please use our google custom search here.

Widget is loading comments...

You can also visit our following web pages on different stuff in math.

**WORD PROBLEMS**

**Word problems on simple equations **

**Word problems on linear equations **

**Word problems on quadratic equations**

**Area and perimeter word problems**

**Word problems on direct variation and inverse variation **

**Word problems on comparing rates**

**Converting customary units word problems **

**Converting metric units word problems**

**Word problems on simple interest**

**Word problems on compound interest**

**Word problems on types of angles **

**Complementary and supplementary angles word problems**

**Markup and markdown word problems **

**Word problems on mixed fractrions**

**One step equation word problems**

**Linear inequalities word problems**

**Ratio and proportion word problems**

**Time and work word problems**

**Word problems on sets and venn diagrams**

**Pythagorean theorem word problems**

**Percent of a number word problems**

**Word problems on constant speed**

**Word problems on average speed **

**Word problems on sum of the angles of a triangle is 180 degree**

**OTHER TOPICS **

**Time, speed and distance shortcuts**

**Ratio and proportion shortcuts**

**Domain and range of rational functions**

**Domain and range of rational functions with holes**

**Graphing rational functions with holes**

**Converting repeating decimals in to fractions**

**Decimal representation of rational numbers**

**Finding square root using long division**

**L.C.M method to solve time and work problems**

**Translating the word problems in to algebraic expressions**

**Remainder when 2 power 256 is divided by 17**

**Remainder when 17 power 23 is divided by 16**

**Sum of all three digit numbers divisible by 6**

**Sum of all three digit numbers divisible by 7**

**Sum of all three digit numbers divisible by 8**

**Sum of all three digit numbers formed using 1, 3, 4**

**Sum of all three four digit numbers formed with non zero digits**