# CBSE Class 10-Mathematics: Chapter –9 Some Applications of Trigonometry Part 7

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**Question 8:**

A round balloon of radius r subtends an angle at the eye of the observer while the angle of the elevation of its center is . Prove that the height of the center of the balloon is .

**Answer:**

In right

In right ,

**Question 9:**

An aeroplane flying horizontally 1 km above the ground is observed at an elevation of . After seconds, its elevation is observed to . Find the speed of the aeroplane in .

**Answer:**

In right ,

In right

Speed