Angles are usually measured using protractors.

角用量角器进行测量。

And he didn't use a protractor to make those perfect letters or any other kind of measurements.

他没有使用量角器或任何其他测量方式来做出那些完美字母。

Protractors have markings on them, similar to rulers, but instead of inches or centimeters it measures in degrees.

量角器上有何直尺类，但是其不是英寸或者是厘米，而是以来衡量。

If you don't have a protractor to measure with, you can estimate how big it is as long as you remember what a 90 degree angle, 180 degree angle, and 360 degree angle look like.

如果你没有量角器，你可以估计它有多大，只要你记得 90 角，180 角和 360 角是什么样子就行了。