A spiral is made up of successive semicircles, with centres alternately at A and B,starting with centre at A, of radii 0.5 cm, 1.0 cm, 1.5 cm, 2.0 cm,

[Hint : Length of successive semicircles is with centres at A, B, A, B, . . .,respectively.]

Solution:Circumference of 1^st semicircle = πr = 0.5π

Circumference of 2^nd semicircle = πr = 1π = π

Circumference of 3^rd semicircle =πr = 1.5π

It is clear that a = 0.5 π, d = 0.5π and n = 13

Hence; length of spiral can be calculated as follows: