Drawing a diagram, we can see that the chord and the radius from the centre to one of the points where it intersects the circle form a right angled triangle with the radius being the hypotenuse.
Using Pythagoras' theorem, we can find the length of this radius:
$r^2 = 6^2 - 3^2$
$r^2 = 27$
$r = \sqrt{27} = 3\sqrt{3}$
Now we can find the angle subtended by the chord at the centre of the circle using the formula:
$\theta = 2\sin^{-1}\left(\frac{\text{chord}}{2r}\right)$
$\theta = 2\sin^{-1}\left(\frac{6}{2\times3\sqrt{3}}\right)$
$\theta \approx 2.06\text{ radians}$
To find the length of the minor arc cut off by the chord, we can use the formula:
$\text{length of arc} = r\theta$
$\text{length of arc} = 3\sqrt{3}\times2.06$
$\text{length of arc} \approx 19.85\text{ cm}$
Therefore, the angle subtended by the chord at the centre of the circle is approximately 2.06 radians, and the length of the minor arc cut off by the chord is approximately 19.85 cm.
In a circle of radius 6cm a chord is drawn 3cm from the centre of the calculate the angle subtended by the chord at the centre of the circle and hence find the length of the minor are cut off by the chord
3 answers
AAAaannndd the bot gets it wrong yet again!
what a lot of work!
cos(θ/2) = 3/6
θ/2 = 60°
θ = 120° = 2π/3 = 2.09 radians
so the arc length is s = rθ = 6 * 2π/3 = 4π = 12.57
You multiplied the chord length by the angle, not the radius.
If the chord has length 2x, then
x^2 = 6^2 - 3^2
x = √27
so the chord has length 2√27 = 10.4
what a lot of work!
cos(θ/2) = 3/6
θ/2 = 60°
θ = 120° = 2π/3 = 2.09 radians
so the arc length is s = rθ = 6 * 2π/3 = 4π = 12.57
You multiplied the chord length by the angle, not the radius.
If the chord has length 2x, then
x^2 = 6^2 - 3^2
x = √27
so the chord has length 2√27 = 10.4
I apologize for the mistake in my previous response. You are correct that the correct method is to use the cosine of half the angle to find the length of the chord, and then use that to find the actual angle.
Using the formula cos(θ/2) = 3/6, we can find the half-angle:
cos(θ/2) = 1/2
θ/2 = 60°
θ = 120° = 2π/3 = 2.09 radians
So the angle subtended by the chord at the centre of the circle is actually 2.09 radians, not 2.06.
Using the formula s = rθ, we can find the length of the minor arc cut off by the chord:
s = 6 * 2.09 = 12.57
So the length of the minor arc cut off by the chord is actually 12.57 cm, not 19.85.
Thank you for bringing this to my attention, and I apologize for any confusion caused by my previous response.
Using the formula cos(θ/2) = 3/6, we can find the half-angle:
cos(θ/2) = 1/2
θ/2 = 60°
θ = 120° = 2π/3 = 2.09 radians
So the angle subtended by the chord at the centre of the circle is actually 2.09 radians, not 2.06.
Using the formula s = rθ, we can find the length of the minor arc cut off by the chord:
s = 6 * 2.09 = 12.57
So the length of the minor arc cut off by the chord is actually 12.57 cm, not 19.85.
Thank you for bringing this to my attention, and I apologize for any confusion caused by my previous response.
3 answers