Cheat sheet

NY Regents Geometry Cheat Sheet

Congruence

27-34%of exam

TransformationsRigid motionsTriangle criteriaConstructionsQuadrilateral proofs

Similarity, Right Triangles, and Trigonometry

29-37%of exam

DilationsSimilarity criteriaRight triangle trigSpecial trianglesLaw of sines/cosines

Circles

2-8%of exam

Inscribed anglesCentral anglesTangentsChords/arcsSector area

Expressing Geometric Properties with Equations

12-18%of exam

Slope/distance/midpointPartitioningLine equationsCircle equationsCoordinate proofs

Geometric Measurement and Dimensions

2-8%of exam

Volume formulasCross-sectionsSolids of rotationSimilar solidsComposite figures

Modeling with Geometry

8-15%of exam

Scale drawingsDensityCapacity/costArea modelingOptimization

Quick Facts

Exam
Geometry Regents
Credential
NY Regents diploma
Time
180 min
Pass
Scale 65
Questions
35 total
Fee
School-administered
Blueprint
6 domains

Congruence Criteria

SSS | SAS | ASA | AAS | HL

SSS: 3 sidesSAS: 2 sides + angleASA: 2 angles + sideAAS: 2 angles + sideHL: hyp + leg

Rigid Motion vs Dilation

Rigid motion

  • Preserves size
  • Translation/reflection/rotation
  • Congruence

Dilation

  • Changes size
  • Scale factor
  • Similarity

Preserves vs scales

Transformation Picker

  1. Slide fixed directionTranslation(Vector)
  2. Flip across lineReflection(Mirror line)
  3. Turn about pointRotation(Center+angle)
  4. Slide then flipGlide reflection(Composition)
  5. Preserves sizeRigid motion(Congruence)
  6. Changes sizeDilation(Similarity)
  7. No motionIdentity(Same image)

Transformations

Translation
Slide by vector
Reflection
Flip over line
Rotation
Turn about point
Glide reflection
Translate then reflect
Rigid motion
Preserves size/shape
Composition
Sequence of motions

Triangle Congruence

SSS
3 sides equalCongruent
SAS
2 sides + included angle
ASA
2 angles + included side
AAS
2 angles + non-included side
HL
Hypotenuse + leg (right)
CPCTC
Parts congruent after proof

Constructions

Copy segment
Compass transfer
Copy angle
Compass arc method
Perpendicular bisector
Equidistant from endpoints
Angle bisector
Equal halves angle
Parallel line
Copy corresponding angle

SohCahToa

Soh | Cah | Toa

Soh: sin=opp/hypCah: cos=adj/hypToa: tan=opp/adj

Congruent vs Similar

Congruent

  • Same size
  • Same shape
  • Rigid motion

Similar

  • Same shape
  • Proportional sides
  • Dilation allowed

Equal vs proportional

Triangle Test Picker

  1. 3 sides equalSSS(Congruent)
  2. 2 sides + included angleSAS(Congruent)
  3. 2 angles + sideASA/AAS(Congruent)
  4. Right + hyp + legHL(Congruent)
  5. 2 angles equalAA(Similar)
  6. 3 proportional sidesSSS~(Similar)
  7. 2 proportional + angleSAS~(Similar)

Similarity

AA~
2 angles equalSimilar
SSS~
3 proportional sides
SAS~
2 proportional + included angle
Dilation
Scale about center
Scale factor
Ratio new/old
Similarity ratio
Side scale factor

Special Right Triangles

45-45-90 | 30-60-90

45-45-90: x | x | x√230-60-90: x | x√3 | 2x

Sine vs Cosine

Sine

  • Opp/hyp
  • Soh
  • Height finder

Cosine

  • Adj/hyp
  • Cah
  • Base finder

Opposite vs adjacent

Right Triangle Trig

Sine
Opp/hypSoh
Cosine
Adj/hypCah
Tangent
Opp/adjToa
45-45-90
Legs equal; hyp = leg√2
30-60-90
x | x√3 | 2x
Geometric mean
Altitude to hypotenuse

General Triangle Trig

Law of Sines
a/sinA = b/sinB
Law of Cosines
c² = a²+b²-2ab cosC
Area formula
½ ab sinC
Ambiguous case
SSA may give 2 triangles
Angle of elevation
Horizontal up to line

Inscribed vs Central Angle

Inscribed

  • Vertex on circle
  • Half arc
  • 2 endpoints

Central

  • Vertex at center
  • Equals arc
  • 2 radii

On circle vs center

Circle Theorems

Inscribed angle
Half intercepted arc
Central angle
Equals intercepted arc
Tangent
Perp to radius
Chord
Endpoints on circle
Secant
Crosses 2 points
Cyclic quadrilateral
Opposite angles sum 180

Circle Measurements

Arc length
(θ/360) × 2πr
Sector area
(θ/360) × πr²
Circumference
2πr or πd
Chord length
2√(r²-d²)
Tangent length
From external point

Distance vs Midpoint

Distance

  • Length between
  • √(Δx²+Δy²)
  • Positive scalar

Midpoint

  • Center point
  • Avg of coords
  • A point

Length vs center

Coordinate Method Picker

  1. Prove parallelCompare slopes(Equal)
  2. Prove perpendicularSlope product = -1(Negative reciprocals)
  3. Find lengthDistance formula(Δx² + Δy²)
  4. Find midpointAvg coordinates(Midpoint formula)
  5. Split segmentPartition ratio(Section formula)
  6. Circle center/radiusComplete the square((x-h)²+(y-k)²=r²)

Coordinate Tools

Slope
(y2-y1)/(x2-x1)
Distance
√(Δx²+Δy²)
Midpoint
Avg of coordinates
Partition
Section formula ratio
Line equation
y = mx + b
Circle equation
(x-h)²+(y-k)²=r²

Coordinate Proofs

Parallel test
Equal slopes
Perpendicular test
Slope product = -1
Right angle test
Perpendicular slopes
Isosceles test
Equal distances
Midsegment
Midpoints of 2 sides

Volume Formulas

Prism=Bh | Cylinder=πr²h | Cone=⅓πr²h

Prism: base×heightCylinder: πr²hCone: ⅓πr²hSphere: 4/3 πr³

Volume vs Surface Area

Volume

  • 3D space
  • Units³
  • Prism = Bh

Surface area

  • Total faces
  • Units²
  • Sum of areas

Inside vs outside

Volume and Solids

Prism
V = BhVolume
Cylinder
V = πr²h
Cone
V = ⅓πr²h
Pyramid
V = ⅓Bh
Sphere
V = 4/3 πr³
Cross-section
Slice of solid shape
Solid of rotation
Spin 2D figure
Similar solids
Vol ratio = k³

Modeling Contexts

Scale drawing
Ratio real/model
Density
Mass per volume
Capacity
Volume held
Area cost
Rate × area
Optimization
Max/min constraints
Composite figure
Sum/subtract parts

Common Traps

Scale Score vs Raw

65 is scaled Not percent correct

Required Tools

Graphing calculator Compass + straightedge

Proof Format

Parts II-IV want reasons Show every step

Similar vs Congruent

Similar = proportional Congruent = equal

Rigid vs Dilation

Rigid preserves size Dilation changes size

Conversion Chart

Each administration differs Use that chart only

Exact vs Approximate

Use exact π key Unless told to round

Last Minute

  1. 1.Big domains: congruence + similarity
  2. 2.35 Q | 80 credits | 3 hours
  3. 3.Pass = scale 65
  4. 4.SSS | SAS | ASA | AAS | HL
  5. 5.SohCahToa = sin/cos/tan
  6. 6.45-45-90 | 30-60-90
  7. 7.Volume: Prism=Bh | Cone=⅓πr²h
  8. 8.Distance + midpoint formulas
  9. 9.Inscribed = ½ arc
  10. 10.Graphing calc + compass required
  11. 11.Show reasons on proofs
  12. 12.Use exact π unless told
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