Step-by-step explanation:
CB is the Hypotenuse of the right-angled triangle CDB.
Pythagoras :
CB² = 20² + 21² = 400 + 441 = 841
CB = sqrt(841) = 29
=> radius = 29/2 = 14.5
the total circumference of the circle (360 degrees) is
2×pi×r = 29×pi
but here we need only the part of the circumference for 180-70= 110 degrees.
CD arc = 29×pi × 110 / 360 = 29×pi×11/36 =
= 27.83800157 ≈ 27.84 cm
