Chapter 10.9, Problem 8PSA

a)

To determine

To find : Circumference of circle with centre O.

Answer to Problem 8PSA

  $62.8$ mm

Explanation of Solution

Given Information :

  

Radius of given circle = $10$ mm

Formula Used:

Circumference of circle = $2\pi r$

Calculation :

Circumference of circle $\odot C=2\times 3.14\times 10$ mm

  $=62.8$ mm

b)

To determine

To find : The angular value of $m(\stackrel{⌢}{\text{AB}})$

Answer to Problem 8PSA

  $72°$

Explanation of Solution

Given Information :

We know that, Length of arc $\stackrel{⌢}{\text{AB}}=4\pi$ mm

Formula Used:

  $m\stackrel{⌢}{\text{AB}}=\frac{\text{arc length × 360°}}{\text{circumference}}$

Calculation:

  $\begin{array}{l}\Rightarrow \frac{4\pi \times 360°}{2\pi r}=m\stackrel{⌢}{\text{AB}}\\ \Rightarrow m\stackrel{⌢}{\text{AB}}=\frac{2\times 360°}{10}\\ \Rightarrow m\stackrel{⌢}{\text{AB}}=72°\end{array}$