## 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