Circle
$A=\pi r^2$
$C=2\pi r$
Right Triangle
$c^2=a^2+b^2$
Cylinder Volume
$V=\pi r^2 h$
Sphere Volume
$V=\tfrac43 \pi r^3$
Cone Volume
$V=\tfrac13 \pi r^2 h$
Sum of Angles
Triangle: 180°
Quadrilateral: 360°
The number of degrees of arc in a circle is 360. The number of radians of arc in a circle is $2\pi$. The sum of the measures in degrees of the angles of a triangle is 180.