Geometry Cheat Sheet 2026

The 30 highest-yield Geometry facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. In logic, a statement and its contrapositive are always: → Logically equivalent
2. The altitude to the hypotenuse of a right triangle creates two smaller triangles that are: → Similar to the original and each other
3. Which of the following can disprove a general conjecture? → A single counterexample
4. If two angles of one triangle equal two angles of another, the triangles are: → Similar
5. What is the volume of a cube with edge length 4? → 64
6. A trapezoid has parallel sides of 6 cm and 10 cm and a height of 4 cm. What is its area? → 32 cm²
7. What is the purpose of a two-column proof? → To organize statements and reasons
8. In a parallelogram, consecutive angles are always: → Supplementary
9. In an isosceles triangle, the altitude from the vertex angle also acts as the: → Perpendicular bisector of the base
10. What is the slope of the line through (0, 0) and (3, 9)? → 3
11. How many faces does an octahedron have? → 8
12. Two similar triangles have areas in the ratio 25:49. Their perimeters are in the ratio: → 5:7
13. What is the circumference of a circle with a diameter of 10 cm? (Use π ≈ 3.14) → 31.4 cm
14. What is the area of a triangle with base 10 and height 6? → 30
15. What is a dilation in geometry? → A proportional resizing
16. What is the sum of the interior angles of a hexagon? → 720°
17. The area of a semicircle with radius 6 is: → 18π
18. A chord is 8 units long and is 3 units from the center. What is the radius (to nearest whole)? → 5
19. The circumference of a circle is 31.4. Using π ≈ 3.14, what is the diameter? → 10
20. Two angles form a linear pair. If one is 105°, what is the other? → 75°
21. What is the volume of a cone with radius 3 and height 4? (use π ≈ 3.14) → 37.68
22. What is the total measure of a straight angle? → 180 degrees
23. A quadrilateral with four equal sides but no right angles is a: → Rhombus
24. If a parallelogram has one angle of 70°, what is the adjacent angle? → 110°
25. If an angle bisector splits a 68° angle, each resulting angle measures what? → 34°
26. How many vertices does a square pyramid have? → 5
27. If the side length of a square is doubled, how does its area change? → It quadruples
28. Reflecting the point (-3, 7) across the y-axis gives? → (3, 7)
29. How many lines of symmetry does a rectangle (non-square) have? → 2
30. The measure of each interior angle of a regular pentagon is: → 108°