NCERT Exemplar Solutions
Class 10 - Mathematics - CHAPTER 8: Introduction to Trignometry and Its Applications - Exercise 8.4
Question 14

Question. 14

From the top of a tower of height \(h\), the angles of depression of two objects in line with the foot are \(\alpha\) and \(\beta\) (with \(\beta>\alpha\)). Find the distance between the objects.

Answer:

Distance \(=h(\cot\alpha-\cot\beta)\).

Detailed Answer with Explanation:

Step 1: Draw a vertical tower of height \(h\). Let the top of the tower be point A and the bottom (foot) be point O.

Step 2: Two objects are lying on the ground in a straight line from O. Let the nearer object be at point P and the farther one at point Q.

Step 3: From the top of the tower (point A), the line of sight to P makes angle of depression \(\beta\) and the line of sight to Q makes angle of depression \(\alpha\).

Step 4: In right-angled triangle AOP:

\(\tan\beta = \dfrac{\text{opposite side}}{\text{adjacent side}} = \dfrac{AO}{OP} = \dfrac{h}{x}\).

So, \(x = h \cot\beta\).

Step 5: In right-angled triangle AOQ:

\(\tan\alpha = \dfrac{AO}{OQ} = \dfrac{h}{y}\).

So, \(y = h \cot\alpha\).

Step 6: The distance between the two objects is:

\(PQ = y - x = h \cot\alpha - h \cot\beta\).

Final Answer: Distance \(= h(\cot\alpha - \cot\beta)\).

NCERT Exemplar Solutions Class 10 – Mathematics – CHAPTER 8: Introduction to Trignometry and Its Applications – Exercise 8.4 | Detailed Answers