Geometry: Lines, Angles & Triangles

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Sniper Mode: Visual Math

1. Lines & Angles

  • Parallel Lines Rules:
    • Z-Rule: Alternate Interior Angles equal.
    • F-Rule: Corresponding Angles equal.
    • C-Rule: Co-Interior angles sum = 180 degree.
  • Linear Pair: Angles on straight line sum 180.
  • Vertically Opposite: X shape. Angles are equal.

2. Triangles (King of Geometry)

  • Sum Property: A+B+C = 180.
  • Exterior Angle: Equal to sum of two opposite interior angles.
  • Centers:
    • Centroid (G): Median intersection. Divides median in 2:1.
    • Incenter (I): Angle bisector intersection. Equidistant from sides.
    • Circumcenter (O): Perpendicular bisector intersection. Equidistant from vertices.
    • Orthocenter (H): Altitude intersection.
  • Congruency: SSS, SAS, ASA, RHS (Exact copy).
  • Similarity: AAA, SSS, SAS (Same shape, different size). Ratio of areas = Ratio of side squares.

3. Circles

  • Tangent: Touches at 1 point. Perpendicular to radius.
  • Chord: Perpendicular from center bisects chord.
  • Angle Property: Angle at center is double the angle at circumference.
  • Cyclic Quadrilateral: Opposite angles sum = 180.