Multiple choice

Angle subtended by a chord AB on the circumference of a circle is 90 degree. If length of chord AB is 16 cm, then what will be radius of this circle?

  1. 8 cm

  2. 9 cm

  3. 12 cm

  4. 10 cm

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

An angle subtended by a chord at the circumference is 90° only if the chord is the diameter of the circle. This is Thales' theorem: the angle in a semicircle is always 90°. Since chord AB subtends 90° on the circumference, AB must be the diameter. Therefore, the radius = diameter/2 = 16/2 = 8 cm. This matches option A.