Question

An arc subtends an angle of 86 at the cir- cumference of a circle whose radius is 8 cm. Find the length of the are to the near- est whole number. (Take = 3.14) (Hint: an angle at the centre = 2x the angle at the circumference).​

Answer 1

We can use the formula for the length of an arc of a circle, which is:

length of arc = (angle/360) × 2πr

where angle is the angle subtended by the arc at the center of the circle, r is the radius of the circle, and π is approximately 3.14.

In this problem, the angle subtended by the arc at the circumference of the circle is 86 degrees. Since the radius of the circle is 8 cm, the diameter is 2 × 8 = 16 cm, and the circumference is 2πr = 2π(8) = 16π cm.

Using the hint given in the problem, we can find the angle subtended by the arc at the center of the circle:

angle at center = 2 × angle at circumference

= 2 × 86

= 172 degrees

Substituting into the formula, we have:

length of arc = (172/360) × 2π(8)

≈ 7.5 cm

Rounding to the nearest whole number, the length of the arc is 8 cm.