Math 1 · Unit 4 · Lesson 2 · part 1 of 6
The Words We Use
The vocabulary for this lesson, in one place.
Words we use
| Word | Plain English | What you do |
|---|---|---|
| Perpendicular | Lines that cross at a right angle, a square corner. | Their slopes are negative reciprocals: multiply them and you get −1. |
| Right angle | A square corner, 90 degrees, like the corner of a page. | Where perpendicular lines meet. |
| Reciprocal | Flip the fraction: the top and bottom swap. The multiplicative inverse from Unit 1. | 23 becomes 32. A whole number 4 is 41, so its reciprocal is 14. |
| Negative reciprocal | Flip the fraction and change the sign. | The slope of a perpendicular line. 23 becomes −32. |
| Product is −1 | Two slopes that multiply to −1. | The quick check for perpendicular. |
| The special pair | A horizontal line (slope 0) and a vertical line (no slope). | They are perpendicular by sight. You cannot flip 0. |