A chord of length 16 units lies in a circle of radius 10 units. How far is the chord from the centre?

1. Draw the line from the centre perpendicular to the chord. 2. That line bisects the chord, so each half is 16 divided by 2, which is 8 units. 3. Now draw a radius to one end of the chord to make a right-angled triangle. 4. The radius of 10 units is the hypotenuse, and one short side is the half chord of 8 units. 5. By the theorem of Pythagoras, the square of the hypotenuse is the sum of the squares of the other two sides. 6. So 10 times 10 is 100, and 8 times 8 is 64, leaving 100 minus 64, which is 36. 7. The distance from the centre is the number whose square is 36, which is 6 units. 8. Answering 8 units gives the half chord rather than the distance from the centre. _Source: Siyavula Mathematics Grade 11 (Everything Maths, CC BY 4.0), Chapter 8: Euclidean geometry_