You need a calculator which has trigonometric functions, or you need a table.
A calculator is the easiest tool to use. Angles can be in degrees or radians, and most calculators allow you to input angles in either degrees or radians, but you may need to put the calculator into the correct mode first. So you input 71.1 and and hit the sin key; or on some calculators you hit sin first and then input the angle. The calculator manual will tell you how to use trig functions.
Before calculators were in popular use, we had to consult tables (usually at the back of a textbook).
The layout of tables was usually whole angles listed in the first column, and the row was divided usually into decimal divisions, so you move along the row up to the column that is headed 0.1 and read off the sine from the body of the table: row 71, column 0.1. Usually you could find what to add if you needed the next decimal place: a small table at the end of the row indicated what to add to the value in the main body of the table. Such lookup tables are rarely required these days because of the widespread, and easier use, of calculators. Tables were usually restricted to an accuracy of only 4 or 5 decimal places, while calculators today are usually have 10 decimal place accuracy. For 10 decimal place accuracy, the tables would require a rather large book and would probably be rather expensive.
Excel also includes trig functions and provides a high degree of accuracy.
sin(71.1°)=0.9461 approximately.