SAT Study Guide/Part 2 - The Math Section/Concepts from Geometry

The SAT generally does not test any arcane or difficult geometry; however, it is important to know several rules.

Degrees and Angles

1. A circle contains 360 degrees. Every circle contains 360 degrees. Each degree is 1/360 of the total distance around the outside of the circle.
2. A line is a 180-degree angle. A line is a flat angle. Half a circle, or a semicircle, is also a 180 degree angle.
3. When two lines intersect, four angles are formed.
4. If two lines are perpendicular, their slopes are negative reciprocals. If line A has a slope of 3, and line B is perpendicular to A, it has a slope of -1/3.
5. When two lines intersect, the angles opposite each other will have the same measures. These are known as vertical angles. The total of all four angles created is 360 degrees.
6. The sum of the lengths of any two sides of a triangle must be larger than the length of the remaining side.
7. A rectangle + two triangles on opposite sides = a trapezoid.