In my opinion ,use trignometry to measure side of trianle as accurate as you desire provided you know measure of at least two angles of triangle.
You can use these two law which is best applicable.
First sine law.
second cosine law
where lower case represent measure of side and upper case rep. angle.
You can measure the sides of a triangle using several tools: centimeter ruler, inch ruler, meter stick, yard stick, etc. It depends soley on personal preference and the scale of the triangle you are measuring. If you meant to ask how to measure the the angles made by the the sides of a triangle, you would use a protractor.