[tex]$AB$[/tex] is a chord of a circle with center [tex]$O$[/tex] and radius [tex]$3 \text{ cm}$[/tex]. If [tex]$\angle OAB = 70^\circ$[/tex], calculate the length of [tex]$AB$[/tex] and the distance from [tex]$O$[/tex] to [tex]$AB$[/tex].



Answer :

Certainly! Let's solve the problem step-by-step.

We are given:

1. The radius of the circle, [tex]\( r = 3 \)[/tex] cm
2. The angle [tex]\( \angle OAB = 70^\circ \)[/tex]

Step 1: Converting the angle from degrees to radians

First, we need to convert the angle [tex]\(\angle OAB\)[/tex] from degrees to radians. The formula to convert degrees to radians is:

[tex]\[ \text{angle in radians} = \text{angle in degrees} \times \left(\frac{\pi}{180}\right) \][/tex]

So,

[tex]\[ \angle OAB_\text{rad} = 70^\circ \times \left(\frac{\pi}{180}\right) \approx 1.2217 \text{ radians} \][/tex]

Step 2: Calculate the length [tex]\( AB \)[/tex]

To find the length of the chord [tex]\( AB \)[/tex], we will use the formula:

[tex]\[ AB = 2 \cdot r \cdot \sin\left(\frac{\theta}{2}\right) \][/tex]

where [tex]\( r \)[/tex] is the radius of the circle, and [tex]\( \theta \)[/tex] is the angle in radians.

Plugging in the given values,

[tex]\[ AB = 2 \cdot 3 \cdot \sin\left(\frac{1.2217}{2}\right) \][/tex]
[tex]\[ AB \approx 2 \cdot 3 \cdot \sin(0.61085) \][/tex]
[tex]\[ AB \approx 2 \cdot 3 \cdot 0.5736 \][/tex]
[tex]\[ AB \approx 3.4415 \text{ cm} \][/tex]

Step 3: Calculate the distance from the center [tex]\( O \)[/tex] to the chord [tex]\( AB \)[/tex]

To find the perpendicular distance from the center [tex]\( O \)[/tex] to the chord [tex]\( AB \)[/tex], we use the formula:

[tex]\[ d = r \cdot \cos\left(\frac{\theta}{2}\right) \][/tex]

Substituting the known values,

[tex]\[ d = 3 \cdot \cos\left(\frac{1.2217}{2}\right) \][/tex]
[tex]\[ d \approx 3 \cdot \cos(0.61085) \][/tex]
[tex]\[ d \approx 3 \cdot 0.8192 \][/tex]
[tex]\[ d \approx 2.4575 \text{ cm} \][/tex]

So, summarizing the results:

- The length of [tex]\( AB \)[/tex] is approximately [tex]\( 3.4415 \)[/tex] cm
- The distance from the center [tex]\( O \)[/tex] to the chord [tex]\( AB \)[/tex] is approximately [tex]\( 2.4575 \)[/tex] cm