ACT Geometry and Trigonometry - Complete Interactive Lesson
Part 1: Angles and Lines
📋 Plane Geometry
Part 1 of 7 — Angles and Lines
Supplementary angles sum to 180°; complementary sum to 90°.
Vertical angles are equal.
Check Your Understanding 🎯
Key Insight: Parallel lines + transversal: alternate interior angles equal, corresponding angles equal.
ACT Tip: Sum of interior angles of an n-gon: (n-2) × 180°.
Check Your Understanding 🎯
Match the Concepts 🔍
Part 2: Triangle Properties
Triangle Properties
Part 2 of 7 — Triangle Properties
Triangle angle sum = 180°.
Triangle inequality: any side < sum of the other two.
Check Your Understanding 🎯
Key Insight: Pythagorean theorem: a² + b² = c² (right triangles only).
ACT Tip: Special right triangles: 30-60-90 (1, √3, 2) and 45-45-90 (1, 1, √2).
Check Your Understanding 🎯
Match the Concepts 🔍
Part 3: Quadrilaterals & Polygons
Quadrilaterals & Polygons
Part 3 of 7 — Quadrilaterals & Polygons
Parallelogram: opposite sides equal and parallel, opposite angles equal.
Rectangle: all angles 90°; Rhombus: all sides equal; Square: both.
Check Your Understanding 🎯
Key Insight: Trapezoid area: ½(b₁ + b₂)h.
ACT Tip: Regular polygon: all sides and angles equal.
Check Your Understanding 🎯
Match the Concepts 🔍
Part 4: Circles
Circles
Part 4 of 7 — Circles
Area = πr²; Circumference = 2πr = πd.
Arc length = (central angle/360°) × circumference.
Check Your Understanding 🎯
Key Insight: Sector area = (central angle/360°) × πr².
ACT Tip: Inscribed angle = half the central angle (same arc).
Check Your Understanding 🎯
Match the Concepts 🔍
Part 5: Area & Perimeter
Area & Perimeter
Part 5 of 7 — Area & Perimeter
Rectangle: A = lw, P = 2l + 2w.
Triangle: A = ½bh.
Check Your Understanding 🎯
Key Insight: Circle: A = πr², C = 2πr.
ACT Tip: Composite figures: break into simple shapes, add/subtract areas.
Check Your Understanding 🎯
Match the Concepts 🔍
Part 6: Problem-Solving Workshop
Problem-Solving Workshop
Part 6 of 7 — Problem-Solving Workshop
Rectangle: A = lw, P = 2l + 2w.
Triangle: A = ½bh.
Check Your Understanding 🎯
Key Insight: Circle: A = πr², C = 2πr.
ACT Tip: Composite figures: break into simple shapes, add/subtract areas.
Check Your Understanding 🎯
Match the Concepts 🔍
Part 7: Review & Applications
Review & Applications
Part 7 of 7 — Review & Applications
Rectangle: A = lw, P = 2l + 2w.
Triangle: A = ½bh.
Check Your Understanding 🎯
Key Insight: Circle: A = πr², C = 2πr.
ACT Tip: Composite figures: break into simple shapes, add/subtract areas.
Check Your Understanding 🎯
Match the Concepts 🔍