Geometry

What you’ll learn

• A scale drawing multiplies every length by the same scale factor $k$; areas scale by $k^2$, not $k$.
• Complementary angles sum to $90°$, supplementary angles sum to $180°$, and vertical angles formed by intersecting lines are equal.
• When a transversal cuts parallel lines, corresponding and alternate interior angles are equal; co-interior angles are supplementary.
• Circumference $C = 2\pi r$ and area $A = \pi r^2$; doubling the radius doubles $C$ but quadruples $A$.
• For a right rectangular prism, $V = \ell w h$ and $SA = 2(\ell w + \ell h + w h)$; for a right cylinder, $V = \pi r^2 h$ and lateral $SA = 2\pi r h$.
• A plane slicing a 3-D figure produces a cross-section whose shape depends on the angle and location of the cut.