does it matter if the angles are named by numbers or letters?

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It doesn't matter really. If you name them with letters, the angles are generally represented as uppercase letters such as A, B, and C while the sides opposite them are the same letter lower case ie: a, b, and c. But numbers or letters will both work fine. You can also use the Greek letter 'theta' to represent an angle: θ.

no, they don't matter.