Chapter 11 - 11.3 - Geometric Sequences and Series - 11.3 Exercises - Page 795: 15

$a_1=1$ $a_2=\frac{1}{2}$ $a_3=\frac{1}{4}$ $a_4=\frac{1}{8}$ $a_5=\frac{1}{16}$

$a_n=a_1r^{n-1}$ $a_1=1,~~r=\frac{1}{2}$ $a_2=1(\frac{1}{2})^{2-1}=1(\frac{1}{2})^1=\frac{1}{2}$ $a_3=1(\frac{1}{2})^{3-1}=1(\frac{1}{2})^2=\frac{1}{4}$ $a_4=1(\frac{1}{2})^{4-1}=1(\frac{1}{2})^3=\frac{1}{8}$ $a_5=1(\frac{1}{2})^{5-1}=1(\frac{1}{2})^4=\frac{1}{16}$