Geometry Cheat Sheet
Geometry Symbols
| ∠, ∠s |
Angle, angles |
| ∠AB |
Measure of angle AB |
 |
Arc AB |
 |
Measure of arc AB |
 |
Circle, circles |
 |
Congruent |
 |
Not congruent |
| ° |
Degree |
| = |
Equal |
| ≠ |
Not equal |
| > |
Greater than |
| < |
Less than |
| AB |
Length of line segment AB |
| AB |
Line AB |
 |
Line segment AB |
 |
Ray AB |
| || |
Parallel |
 |
Not parallel |
 |
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 |
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