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Math 8
Triangles and Transversals
| Term | Definition |
|---|---|
| Angles of a triangle | add up to 180 degrees |
| Straight line | 180 degrees |
| How to find a missing angle INSIDE a triangle | x + x + x = 180 30 + 42 + x= 180 72 + x = 180 -72 -72 x = 108 degrees So, add the two known INTERIOR angles and subtract from 180. |
| How to find a missing angle OUTSIDE a triangle | Exterior angle = Remote interior + remote interior x = 30 + 42 x = 72 degrees So, add the two REMOTE INTERIOR angles. DO NOT SUBTRACT FROM 180!!! |
| Remote interior angle | Two interior angles NOT NEXT TO or across from the exterior angle. |
| Alternate Interior Angles | Congruent angles formed by parallel lines cut by a transversal that are both between the parallel lines and on opposite sides of the transversal line. |
| Alternate Exterior Angles | Congruent angles formed by parallel lines cut by a transversal that are both outside the parallel lines and on opposite sides of the transversal line. |
| Corresponding Angles | Congruent angles formed by parallel lines cut by a transversal that are both on the same side of the transversal line but one is between the parallel lines while the other is outside the parallel lines. |
| Vertical Angles | Congruent angles formed by parallel lines cut by a transversal that share a vertex. These are across a vertex from each other and form a "bow tie". |
| Congruent Angles | Angles that are the same degrees. |
| Complementary Angles | Two or more angles that form a right angle (add up to 90 degrees). |
| Supplementary Angles | Two or more angles that form a straight angle (add up to 180 degrees). |
| Consecutive Interior Angles or Same Side Interior | Supplementary angles formed by parallel lines cut by a transversal that are both on the same side of the transversal line and between the parallel lines. One will be acute and one will be obtuse. |
| Consecutive Exterior Angles or Same Side Interior | Supplementary angles formed by parallel lines cut by a transversal that are both on the same side of the transversal line and outside the parallel lines. One will be acute and one will be obtuse. |
| Adjacent (Linear Pair) Angles | Supplementary angles formed by parallel lines cut by a transversal that are next to each other. They will share a vertex and ray. One will be acute and one will be obtuse. |
| Right Angle | 90 degree angle |
| Acute Angle | an angle that is < 90 degrees |
| Obtuse Angle | an angle that is > 90 degrees and < 180 degrees |
| Straight Angle | 180 degree angle |
| Parallel Lines | Lines that run next to each other and never intersect. |
| Transversal Line | Line that crosses two or more parallel lines. |
| Perpendicular Lines | Lines that cross at a 90 degree angle. |
| How to find a missing supplementary angle | Write the equation x + known angle = 180, then subtract the known angle from both sides |
| How to solve a multistep equation | 1. distribute (parentheses- multiply) 2. combine like terms (same side, add) 3. move (+ or -) the variable with the smaller coefficient to get variables on one side 4. move (+ or -) the constant on the side with the remaining variable to get constants on one side 5. multiply or divide by coefficient to get x by itself |