Geometry

learning_notes

Last updated: 8/16/2025

Lines, Angles, and Triangles

Key Concepts

  • Angle types: complementary, supplementary, vertical, adjacent
  • Triangle types: equilateral, isosceles, scalene
  • Triangle angle sum = 180°
  • Exterior angle theorem

Skills Tested

  • Solving for unknown angles
  • Applying triangle properties
  • Using algebra with geometric relationships

Example Question

In a triangle, two angles measure 40° and 65°. What is the third angle? A. 75° B. Answer: 75° (Because 180 - 40 - 65 = 75)

Triangle Properties and Theorems

Key Concepts

  • Pythagorean theorem: a^2 + b^2 = c^2
  • Special right triangles:
    • 45-45-90: sides are x, x, x\sqrt{2}
    • 30-60-90: sides are x, x\sqrt{3}, 2x
  • Area = \frac{1}{2} \text{base} \times \text{height}
  • Triangle Inequality: sum of two sides > third side

Skills Tested

  • Finding side lengths
  • Solving for unknowns using triangle rules
  • Applying special triangle patterns

Example Question

What is the hypotenuse of a right triangle with legs 6 and 8? A. 10 B. Answer: 10 (Use a^2 + b^2 = c^2: 36 + 64 = 100 \Rightarrow c = \sqrt{100} = 10)

Circles

Key Concepts

  • Radius, diameter, circumference, area
    • Circumference: C = 2\pi r
    • Area: A = \pi r^2
  • Arcs, sectors, and central angles
  • Equations of circles: (x - h)^2 + (y - k)^2 = r^2

Skills Tested

  • Calculating arc lengths and areas of sectors
  • Working with circle equations
  • Finding center and radius from equation

❓ Example Question

What is the area of a circle with diameter 10? A. 25\pi B. Answer: 25\pi (Radius = 5; area = \pi(5)^2)

Polygons

Key Concepts

  • Sum of interior angles: (n - 2) \times 180^\circ
  • Each angle in regular polygon: \frac{(n - 2) \times 180^\circ}{n}
  • Properties of quadrilaterals (parallelograms, rectangles, trapezoids)

Skills Tested

  • Finding missing angles
  • Identifying shape properties
  • Working with side/angle relationships

Example Question

What is the sum of the interior angles of a hexagon? A. 720° B. Answer: 720° (6 sides → (6 - 2) \times 180 = 720^\circ)

Solid Geometry (3D)

Key Concepts

  • Volume and surface area formulas:
    • Rectangular prism: V = lwh, SA = 2lw + 2lh + 2wh
    • Cylinder: V = \pi r^2 h
    • Sphere: V = \frac{4}{3}\pi r^3
    • Cone: V = \frac{1}{3} \pi r^2 h
  • Cross-sections and nets

Skills Tested

  • Calculating volume and surface area
  • Understanding 3D shape features
  • Solving word problems involving shape dimensions

Example Question

What is the volume of a cylinder with radius 3 and height 4? A. 36\pi B. Answer: 36\pi (Volume = \pi r^2 h = \pi(9)(4) = 36\pi)

Coordinate Geometry & Distance

Key Concepts

  • Distance formula: \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}
  • Midpoint formula: \left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2} \right)
  • Slope and equations of lines
  • Using coordinates to verify geometric relationships

Skills Tested

  • Finding lengths, midpoints, and slopes
  • Verifying right angles or congruent segments
  • Applying geometric properties in the coordinate plane

Example Question

What is the distance between (3, 4) and (6, 8)? A. 5 B. Answer: 5 (Use distance formula: \sqrt{(6 - 3)^2 + (8 - 4)^2} = \sqrt{9 + 16} = \sqrt{25} = 5

Features

  • Aris - 1on1 AI tutor
  • Skills Tree
  • Improvement analytics
  • Error-Hacking Vault
  • Special topics
logoAris Tutor

ArisTutor is powered by a group of standardized test prep experts from top-tier colleges who aspire to help more students get high-quality ACT, AP and SAT prep resources at a fraction of the cost of premium tutors.

SAT® and AP® are trademarks registered by the College Board, which is not affiliated with, and does not endorse, this product.
ACT® is a trademark registered by the ACT, Inc, which is not affiliated with, and does not endorse, this product.