Help with ACT Geometry Formulas?

Hey everyone, I'm struggling a bit with geometry on the ACT. Can anyone recommend some essential geometry formulas I should know for the test? Thanks in advance!

Hi! Geometry can indeed be a bit tricky on the ACT, but having a grasp on some essential formulas will definitely help you. Here's a list of important geometry formulas you should be familiar with for the test:

1. Area of a rectangle: A = length × width

2. Area of a triangle: A = (base × height) / 2

3. Area of a parallelogram: A = base × height

4. Area of a trapezoid: A = (base1 + base2) × height / 2

5. Area of a circle: A = π × (radius)^2

6. Circumference of a circle: C = 2 × π × radius

7. Length of an arc: Arc = (angle/360) × circumference

8. Area of a sector: Area = (angle/360) × (π × (radius)^2)

9. Pythagorean theorem: a^2 + b^2 = c^2 (for right triangles)

10. Triangle angle sum: The sum of all angles in a triangle equals 180°

11. Supplementary angles: The sum of two supplementary angles is 180°

12. Complementary angles: The sum of two complementary angles is 90°

13. Volume of a rectangular prism: V = length × width × height

14. Volume of a cylinder: V = π × (radius)^2 × height

15. Volume of a cone: V = (1/3) × π × (radius)^2 × height

16. Volume of a sphere: V = (4/3) × π × (radius)^3

17. Surface area of a rectangular prism: SA = 2lw + 2lh + 2wh

18. Surface area of a cylinder: SA = 2πrh + 2πr²

As you prepare for the ACT, make sure you don't just review these formulas, but also practice applying them in different contexts, including word problems. Also pay special attention to any that you find particularly difficult so you can work on your weak points. And, if you're having trouble grasping any of them, reaching out to your school's geometry teacher (even if you haven't taken geometry yet) could be a good idea, and they've likely helped many past students prep for the geometry concepts on the ACT.

Best of luck!