How to use clark's table?

How to use clark’s table???

In the required quantity on the table, you are mensioned angle and its value (say tan) next to it
Eg for tan 450 = 1
and for tan 45015’ search for colunm closest to 15’ it is 12’ then add look in mean diferences table
and find for what u have to add to make it 15
it is 3’
thus the value of tan 45015’= 1.0000+0.0070+0.0013