180∘
Key Idea: Sum of Angles in a Triangle
The sum of the interior angles of any triangle is always:
180∘
General Rule:
Angle 1+ Angle 2+ Angle 3 = 180∘
Applies to all triangles: scalene, isosceles, and equilateral.
Can be used to find a missing angle if the other two are known.
Why this matters for the SAT:
Triangle angle sums appear frequently in geometry problems.
Knowing this rule allows you to quickly solve for missing angles and check your work.
Sum of angles that split a straight line is 180.
Key Idea: Supplementary Angles
Supplementary angles are two angles whose sum is 180°.
They often appear as angles that form a straight line.
General Rule:
Angle 1 + Angle 2 = 180∘
Each angle is called the supplement of the other.
Can be used to find a missing angle when one is known.
Why this matters for the SAT:
Supplementary angles frequently appear in geometry problems, including lines, triangles, and polygons.
Recognizing this relationship helps solve for unknown angles quickly.
180∘
Radians and degrees are two ways to measure angles.
1 radian=(180∘/π)≈57.3
SAT problems may give angles in radians or degrees. Knowing how to convert between them is essential for trigonometry, unit circle, and angle-measure problems.
