Symbols in Geometry

Common Symbols Used in Geometry

Symbols save time and space when writing. Here are the most common geometrical symbols:

Symbol Meaning Example In Words
Triangle △ABC has 3 equal sides Triangle ABC has three equal sides
Angle ∠ABC is 45° The angle formed by ABC is 45 degrees.
Perpendicular AB⊥CD The line AB is perpendicular to line CD
Parallel EF∥GH The line EF is parallel to line GH
° Degrees 360° 360 degrees (a full rotation!)
∟  Right Angle (90°) ∟ is 90° A right angle is 90 degrees
line segment AB Line Segment "AB" AB The line segment between A and B
line AB Line "AB" line AB The infinite line that includes A and B
ray AB Ray "AB" ray AB The line that starts at A, goes through B and continues on
Congruent (same shape and size) △ABC ≅ △DEF
Triangle ABC is congruent to triangle DEF
Similar (same shape, different size) △DEF∼△MNO Triangle DEF is similar to triangle MNO
Therefore a=b therefore b=a a equals b, therefore b equals a

Example: In △ABC, ∠BAC is ∟

Is really saying: "In triangle ABC, the angle BAC is a right angle"

angle abc

Naming Angles

For angles the central letter is where the angle is.

Example: ∠ABC is 45°

The point "B" is where the angle is.


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