Geometry Symbols
| ∠, ∠s | Angle, angles |
| ∠AB | Measure of angle AB |
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Arc AB |
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Measure of arc AB |
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Circle, circles |
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Congruent |
 |
Not congruent |
| ° | Degree |
| = | Equal |
| ≠ | Not equal |
| > | Greater than |
| < | Less than |
| AB | Length of line segment AB |
| AB | Line AB |
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Line segment AB |
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Ray AB |
| || | Parallel |
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Not parallel |
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Parallelogram |
| ⊥ | Perpendicular |
| ˜ | Similar |
| δ | Triangle |
| (x, y) | Ordered pair in plane |
| a⁄b = c⁄d | Proportion |
| a: b or a⁄b | Ratio |
Useful Abbreviations
| AA | Angle-angle, for proving triangles similar |
| AAS | Angle-angle-side, for proving triangles congruent |
| ASA | Angle-side-angle, for proving triangles congruent |
| cos | Cosine |
| cot | Cotangent |
| CPCTC | Congruent parts of congruent triangles are congruent |
| csc | Cosecant |
| CSSTP | Corresponding sides of similar triangles are proportional |
| SAS | Side-angle-side, for proving triangles congruent |
| sin | Sine |
| tan | Tangent |
Common Variables
| a | Apothem |
| a, b, c | Lengths of the sides of a triangle |
| A | Area of a polygon |
| B | Area of the base of a solid |
| C | Circumference of a circle |
| h | Height of an altitude |
| α | Alpha (name of an angle) |
| β | Beta (name of an angle) |
| X1 x | Unknown value |
| θ | Theta (name of an angle) |
| π | Pi |
| Slant length of a side of a solid | |
| l or l | Length of a rectangle |
| L | Lateral area of a solid |
| m | Slope of a line |
| M | Midpoint of a line segment |
| n | Number of sides of a polygon |
| P | Perimeter of a polygon |
| P or P' | Plane |
| r | Radius |
| s | Length of the side of an equilateral polygon |
| S | Surface area of a solid |
| T | Total area |
| V | Volume |
| w or w | Width of a rectangle |
Formulas You Should Know
| Area | (A) of a triangle A = ½bh where b measures the base and h the altitude |
| Perimeter | (P) of a triangle P = a + b + c where a, b, and c are the lengths of the sides |
| Area | (A) of a rectangle A = lw where l measures the length and w the width |
| Perimeter | (P) of a rectangle P = 2b + 2h where b measures the width and h the height |
| Area | (A) of a circle A = πr2 where r measures the radius |
| Area | Circumference (C) of a circle C = 2πr or C = πd where r measures the radius and d the diameter |
