# Important Formulas

You should know these formulas by heart.

Some of these have different versions floating around.

I strongly recommend you use these versions.

# Areas of Shapes

Area of a Triangle

$$A = \frac{b × h}{2}$$

Area of a Trapezium

$$A = \frac{a + b}{2} × h$$

Area of a Circle

$$A = \pi r^2$$

Circumference of a Circle

$$C = \pi D$$

Pythagoras’ Theorem

$$a^2 + b^2 = c^2$$

$$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$$