The tops of two poles of height 22 m and 31 m are connected by a wire. If the wire makes an angle of 60° with the horizontal, then the length of the wire (in m) is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → $6\sqrt{3}$
1. Identify the Vertical Difference
The two poles have heights of 31 m and 22 m. When a wire connects the tops, the vertical distance ($h$) between the two tops is the difference in their heights:
$h = 31\text{ m} - 22\text{ m} = 9\text{ m}$
2. Form a Right-Angled Triangle
Imagine a horizontal line drawn from the top of the shorter pole (22 m) to the taller pole (31 m). This forms a right-angled triangle where:
- The Perpendicular ($P$) is the height difference: 9 m.
- The Hypotenuse ($L$) is the length of the wire (which we need to find).
- The Angle of elevation ($\theta$) with the horizontal is 60°.
3. Apply Trigonometry
We use the sine function, which relates the perpendicular and the hypotenuse:
$\sin(\theta) = \frac{\text{Perpendicular}}{\text{Hypotenuse}}$
$\sin(60^\circ) = \frac{9}{L}$
Since $\sin(60^\circ) = \frac{\sqrt{3}}{2}$, we substitute the value:
$\frac{\sqrt{3}}{2} = \frac{9}{L}$
4. Solve for $L$
$L = \frac{9 \times 2}{\sqrt{3}}$
$L = \frac{18}{\sqrt{3}}$
To rationalize the denominator, multiply the numerator and denominator by $\sqrt{3}$:
$L = \frac{18 \times \sqrt{3}}{3}$
$L = 6\sqrt{3}$
Final Answer:
The length of the wire is $6\sqrt{3}$ m.