Dividend Policy – residual theory

there is a worked example of which i dont understand one part:

a firm pays 10c constant dividend at a cost of equity of 10%

pv= 10/.1=100c

if at T1 the div is not paid, it will be due on T2 and it will be worth 11c

so

T0————-T1—————-T2———————–T3
——————0—————10,11——————-10

in calculating pv in this case, the working is shown as:

pv= 10 + 11/1.1^2 + (10/0.1 x (1/1.1^2))

i dont understand why 10 is being added. if at T2 the dividends are 10 plus 11, then why isnt it 21/1.2^2?

regards